VIEQUES, Puerto Rico—The U.S. Navy ceased military training operations on this small island in 2003, and windows no longer rattle from the shelling from ships and air-to-ground bombings.

Gone are the protests that drew celebrities like Benicio Del Toro and Robert F. Kennedy Jr. Real estate prices and tourism have boomed: a 157-room Starwood W hotel is expected to open by December on the island, which is seven miles east of Puerto Rico's mainland.

But Vieques, once the largest training area for the U.S. Atlantic Fleet Forces, is still largely defined by its old struggles. Once again, residents have squared off against the U.S. military.

The Navy has begun removing hazardous unexploded munitions from its old training ground by detonating them in the open air. It also proposes to burn through nearly 100 acres of dense tropical vegetation to locate and explode highly sensitive cluster bombs.

But what could have been a healing process has been marred by lingering mistrust. As the Navy moves to erase a bitter vestige of its long presence here, residents assert that it is simply exposing them again to risk.

“;The great majority of emergency room visits here last year were for respiratory problems,”; said Evelyn Delerme Camacho, the mayor of Vieques. “;Can they guarantee that contaminants or smoke won't reach the population? Would we have to wait and see if there's a problem?”;

The cleanup comes as the local Vieques government and most of the island's 9,300 residents pursue claims against the U.S. government for contamination and for illnesses that they assert are linked to pollutants released during decades of live-fire and bombing exercises beginning in World War II.

Given the history of grievances, many locals are aghast that the Navy's methods involve burnings and detonations whose booms can be heard in some residential areas, setting people on edge. They have spoken out at public hearings and in legislative resolutions.

But Christopher T. Penny, head of the Navy's Vieques restoration program, said the unexploded bombs were too powerful to be set off in detonation chambers. And he said that experiments to cut through the dense vegetation with a remote-control device had not had much success.

Environmental Protection Agency officials who are overseeing the project say that such on-site detonations are typical of cleanups at former military training ranges. Jose C. Font, an EPA deputy director in San Juan, say they pose no threat to human health as long as limited amounts are exploded each time, the wind is calm and air quality is monitored constantly.

In 2005 the training ground was designated a federal Superfund site, giving the EPA the authority to order a cleanup led by the party responsible for the pollution.

The unexploded munitions lie on 8,900 acres of former Navy land on the eastern end of the island, including 1,100 acres of what was once the live impact area. The EPA says the cleanup could take 10 years or more.

Workers are using historical records, aerial photography and high-power metal detectors to locate the munitions before cutting through the foliage and detonating them. So far, the Navy says, it has identified 18,700 munitions and explosives and blown up about a third of those.

The EPA says that the hazardous substances associated with ordnance that may be present in Vieques include TNT, napalm, depleted uranium, mercury, lead and other chemicals, including PCBs.

Residents' concerns about the cleanup are heightened by suspicions of a link between the contaminants and what Puerto Rico's health department found were disproportionately high rates of illnesses like cancer, hypertension and liver disease on the island.

In 2003, the U.S. Agency for Toxic Substances and Disease Registry, which assesses health hazards at Superfund sites, concluded that levels of heavy metals and explosive compounds found in Vieques' soil, groundwater, air and fish did not pose a health risk.

But this year the registry agency said it would “;rigorously”; revisit its 2003 finding, and its director, Dr. Howard Frumkin, plans to visit Vieques on Wednesday to meet with residents.

Puerto Rico's legislature, meanwhile, has asked President Barack Obama to keep a campaign promise “;to achieve an environmentally acceptable cleanup”; and “;closely monitor the health of the people of Vieques and promote appropriate remedies.”;

Most contested here is a Navy request to the EPA and the Environmental Quality Board in Puerto Rico to allow the controlled burn to clear vegetation and find bombs. The risk of accidental explosions, the Navy says, is too high for workers to do it by hand using chainsaws, machetes and trimmers.

“;The issue is safety,”; said Penny of the Navy. Many residents complain that they have not received enough information to feel reassured. Among them are a group that gathers on most evenings in a plaza of sand-colored buildings anchored by the church in Isabel Segunda, Vieques' main town.

“;We hear they are taking out bombs, but we haven't been informed of what exactly is coming out of there and whether there's more contamination when they get it out,”; said Julio Serrano, 57, who works at the airport as an operations supervisor. “;We need to be told clearly what's in there.”;

Yet some experts on military cleanups suggest that, rather than focusing on any short-term air quality problems, residents might consider the possibility of an accidental explosion that is years away.

“;The real risk is that there's no technology available that would guarantee that they've removed every piece of ordnance,”; said Jacqueline MacDonald Gibson, an assistant professor of environmental sciences and engineering at the University of North Carolina in Chapel Hill who has studied the risks of adapting former training ranges. “;There's no way to make that land safe for reuse unless it's very restrictive.”;

Other battles loom. Most of the 26,000 acres the Navy used to own on the eastern and western ends of Vieques—making up about three-fourths of the island—have been turned over to the Department of the Interior, which plans to maintain the land as a wildlife preserve.

The Fish and Wildlife Service has already opened up small portions of the area to the public as a wildlife refuge that includes gorgeous undeveloped beaches where sea turtles like the loggerhead and hawksbill nest.

But Mayor Delerme Camacho said that once the cleanup is over, Vieques' residents want to be able to use the land for housing and ecotourism, too. Already, those eager to build have staked out makeshift claims with signs on trees within a chunk of 4,000 acres transferred by the Navy to the municipal government.

Though fishermen can now catch red snapper and yellowtail unfettered by the Navy's target practice, and visitors have discovered the rural charms of a place where horses roam freely on the roads, Vieques still has high rates of poverty and lacks a full-fledged hospital.

Ismael Guadalupe, 65, a retired teacher and leader in the long resistance to the Navy's operations here, said that while the training is over, the fighting continues. “;As one of our sayings goes, 'If we had to eat the bone, now we should be able to eat the meat,”;' he said.