DETROIT—The 911 call came at 6:35 p.m. on Aug. 28 from a car that was speeding out of control on Highway 125 near San Diego.

The caller, a male voice, was panic-stricken: “;We're in a Lexus ... we're going north on 125 and our accelerator is stuck ... we're in trouble ... there's no brakes ... we're approaching the intersection ... hold on ... hold on and pray ... pray ...”;

The call ended with the sound of a crash.

The Lexus ES 350 sedan, made by Toyota, had hit a sport utility vehicle, careened through a fence, rolled over and burst into flames. All four people inside were killed—the driver, Mark Saylor, an off-duty California Highway Patrol officer, and his wife, daughter and brother-in-law.

It was the tragedy that forced Toyota, which had received more than 2,000 complaints of unintended acceleration, to step up its own inquiry, after going through multiple government investigations since 2002.

Yet only last week did the company finally appear to come to terms with the scope of the problem, after expanding a series of recalls to cover millions of vehicles around the world, incalculable damage to its once-stellar reputation for quality and calls for congressional hearings.

With prodding from the National Highway Traffic Safety Administration, Toyota halted production and sales of eight models, including its top-selling Camry sedan.

And late last week, the government allowed the company to go ahead to try yet another new fix for its vehicles, which it is expected to announce Monday.

At almost every step that led to its current predicament, Toyota underestimated the severity of the sudden-acceleration problem affecting its most popular cars. It has veered from discounting early reports of problems to overconfidently announcing diagnoses and insufficient fixes.

The effect on Toyota's business is already being felt. Its sales in the United States in January are expected to drop 11 percent from a year earlier, and its market share in the United States is likely to fall to its lowest point since 2006, according to Edmunds.com, an automotive research Web site.

The company has not yet projected the cost of its recalls and lost sales. But a prolonged slowdown in sales could substantially hurt a company that once minted profit.

As recently as the fall, Toyota was still saying it was confident that loose floor mats were the sole cause of any sudden acceleration, issuing an advisory to millions of Toyota owners to remove them. The company said on Nov. 2 that “;there is no evidence to support”; any other conclusion, and added that its claim was backed up by the federal traffic safety agency.

But, in fact, the agency had not signed on to the explanation, and it issued a sharp rebuke. Toyota's statement was “;misleading and inaccurate,”; the agency said. “;This matter is not closed.”;

Toyota's handling of the problem is a story of how a long-trusted carmaker lost sight of one of its bedrock principles.

In Toyota lore, the ultimate symbol of the company's attention to detail is the “;andon cord,”; a rope that workers on the assembly line can pull if something is wrong, immediately shutting down the entire line. The point is to fix a small problem before it becomes a larger one.

But in the broadest sense, Toyota itself failed to pull the andon cord on this issue, and treated a growing safety issue as a minor glitch—a point the company's executives are now acknowledging in a series of humbling apologies.

“;Every day is a lesson, and there is something to be learned,”; Yoshimi Inaba, Toyota's top executive in North America, said at the Detroit auto show in January. “;This was a hard lesson.”;

In Davos, Switzerland, on Friday, Akio Toyoda, the grandson of Toyota's founder who now heads the company, told a Japanese broadcaster that he was “;deeply sorry”; for the recalls.

Toyota's safety problems may prove to be a hard lesson for the NHTSA, as well. Six separate investigations were conducted by the agency into consumer complaints of unintended acceleration, and none of them found defects in Toyotas other than unsecured floor mats.

In at least three cases, the agency denied petitions for further investigative action because it did not see a pattern of defects and because of a “;need to allocate and prioritize NHTSA's limited resources”; elsewhere, according to agency documents.

The investigations, and Toyota's handling of the problem, will be the subject of congressional hearings.

But the publicity surrounding the accident near San Diego, and Toyota's repeated inability to quell consumer concerns with a definitive solution, has also prompted a flood of lawsuits reminiscent of the litigation a decade ago arising out of the rollovers of Ford Explorers equipped with Firestone tires.

In addition to cases related to individual accidents, several class-action suits have been filed against Toyota. The cases are expected to focus on why the government and the carmaker were unable to identify problems beyond the floor mats, despite mounting instances of runaway cars.

David Ennis, a Washington lawyer, said he was working on three lawsuits that had been in the works for five months. “;Over the last 24 hours, everybody's a Toyota lawyer now,”; he said last week.

Toyota now believes that the trouble with its cars is twofold—a combination of loose floor mats that can interfere with accelerator pedals, and a pedal that itself can stick when a driver depresses it.

Toyota has told its dealers that it will announce its fix for the faulty accelerators on Monday, but has yet to release details. The CTS Corp., the supplier of the pedals used in recalled models, is making replacement parts. But Toyota is also expected to try to repair or modify the pedals in some vehicles.

Before last August, Toyota had issued three limited recalls to replace floor mats and change an interior part that could catch on accelerator pedals.

But after the fatal crash near San Diego, and the public release of the 911 tape, Toyota was forced to, as it said in the fall, “;take a closer look.”; That crash, said Clarence M. Ditlow, executive director of the Center for Auto Safety in Washington, “;was a watershed event.”;

“;It captured on tape the deaths of four people in an uncontrolled acceleration where the driver was an experienced highway patrol officer,”; he said. “;If he couldn't bring the car under control, who could?”;

A lawyer for the Saylor family said he wished that the federal government had acted more quickly about concerns over the sudden acceleration.

“;They're clearly starting to become more interested in the problem and more attentive to it,”; said the lawyer, John Gomez, of San Diego. “;Do I wish they would have done more sooner? Obviously.”;

In one federal inquiry on Toyota models built from 2002 to 2005, investigators found that 20 percent of the 432 complaints studied involved “;sudden or unintended acceleration.”;

But no defects were uncovered in any of the vehicles, and the rate of incidents was considered “;unremarkable”; in the context of the millions of cars on the road.

The petitioner in that case, Jordan Ziprin of Phoenix, said the regulators had focused exclusively on mechanical issues with his car, a 2002 Camry.

“;I believe this is an electronic issue, but they have been avoiding that possibility entirely,”; Ziprin said in an interview.

Several lawsuits against Toyota also suggest that the company's electronic system could be at fault.

A Toyota spokesman said the company had looked extensively at its computerized electronic throttle system, which controls the speed of its cars, and had found no faults.

“;If we found anything, we would take appropriate action,”; said the spokesman, Mike Michels. “;But we continue to think it's entirely unlikely that an electronic malfunction is the cause.”;

A lawyer for a California man whose wife died in a 2007 crash of a Camry said the company was avoiding a potentially more pervasive problem by focusing on mats and stuck pedals, rather than its electronics.

“;There are thousands of these complaints, and we're not seeing floor mats and we're not seeing stuck throttles,”; said the lawyer, Donald H. Slavik, of Milwaukee, Wis. The traffic safety agency “;simply doesn't have the resources to analyze the electronic systems of these cars.”;

The agency, which is part of the Transportation Department, has stepped up its oversight of Toyota drastically since the fatal accident that involved the Saylor family.

Agency officials, who spoke on condition of anonymity because the case was still being investigated, say their responsibility is to identify defects in autos, not to develop remedies to fix them. That responsibility, these officials said, rests with the automaker.

Many complaints by consumers were eliminated by the agency during its investigations because of possible driver error, or the lack of sufficient information about the circumstances of the incidents.

The agency separated braking problems from acceleration issues, further narrowing the number of complaints that could be linked to a faulty pedal or an electronic malfunction. Cases involving brief periods of acceleration were also considered separately from those that involved prolonged, high-speed incidents, many of which involved accidents.

Sean Kane, whose consulting firm, Safety Research and Strategies, counts plaintiffs' lawyers among its clients, contends that the agency did not push Toyota for more data, and too quickly accepted the company's explanations about floor-mat problems.

“;The agency has not been very forceful with Toyota at all,”; Kane said. The agency “;always took the low-hanging fruit for an explanation, which is the floor mat.”;

The discussions between federal officials and Toyota intensified in December, when the acting chief of the agency, Ronald Medford, flew to Japan to hold meetings with senior company executives, according to a government official with knowledge of the trip who was not authorized to speak publicly.

On Jan. 19, two days before the recall for the sudden-acceleration problem, Inaba of Toyota met in Washington with Medford and the new head of the agency, David Strickland.

The mounting number of complaints and accidents has led the agency to be more outspoken than it usually is during ongoing investigations.

Last week, the transportation secretary, Ray LaHood, said in an interview with a Chicago radio station that Toyota had halted production of recalled vehicles “;because we asked them to.”;

Indeed, Toyota had to be told by regulators to shut down production and suspend sales of the cars and trucks in the latest recall until it had the parts necessary to fix them. It was yet another example of a slow response from a company long known for its meticulous approach to building cars and servicing customers.

Michels, the Toyota spokesman, said the company had never before had to halt production or stop selling millions of vehicles involved in a recall.

“;It's not a typical case,”; he said. “;Usually in a 'stop sale' it's a very small quantity.”;

In its attempts to play down the problem, Toyota may have raised more doubts among consumers.

“;It thinks it can control this crisis, and in the process has thrown its own credibility out the window,”; said Kane, the safety consultant whose firm has documented thousands of reports of unintended acceleration.

Some owners of recalled Toyotas are now saying they are afraid to drive them. “;I live only a half mile from the office and I drive there,”; said Elaine Byrnes, a Camry owner in Los Angeles. “;If I had to go farther, I wouldn't consider it.”;

And the scrutiny of Toyotas will not end with its new plan to replace the pedals. Accidents are receiving swift attention from federal regulators.

On Dec. 26, a 2008 Toyota Avalon—one of the cars under recall—crashed just outside of Dallas. A police officer in Southlake, Texas, Roderick Page, said in an interview that “;for undetermined reasons, the vehicle left the main roadway, and went through a metal pipe fence, striking a tree and causing the vehicle to flip and land upside down in a pond.”;

All four people in the car died. “;There was no evidence that they attempted to hit the brake or slow down,”; he said. “;Honestly, my reaction is, 'Wow.”;'

Two weeks later, an investigator from the National Highway Traffic Safety Administration visited Southlake to inspect the car, accompanied by a Toyota engineer. Page said one factor they immediately ruled out was the floor mats, which were in the trunk.

Matt Richtel contributed reporting from San Francisco, Clifford Krauss from Houston and Matthew L. Wald from Washington.