More than one in 10 deaths in immigration detention in the last six years have been overlooked and were omitted from an official list of detainee fatalities issued to Congress in March, the Obama administration said Monday.

The administration added 10 previously unreported deaths to the official roster and disclosed an 11th, which occurred Friday: that of Huluf Guangule Negusse, a 24-year-old Ethiopian. Negusse died from the effects of an Aug. 3 suicide attempt in the Wakulla County correctional facility near Tallahassee, Fla.

What Immigration and Customs Enforcement officials call “;the death roster”; stands at 104 since October 2003, up from the 90 that were on the list the agency gave to Congress this spring.

The latest search for records was undertaken late last month, officials said, when Freedom of Information litigation by the American Civil Liberties Union uncovered one of the 10 deaths that had gone unreported — that of Felix Franklin Rodriguez-Torres, 36, an Ecuadorean who settled in New York and died of testicular cancer on Jan. 18, 2007, after being detained two months at an immigration jail run for profit by Corrections Corporation of America in Eloy, Ariz.

On Saturday, after inquiries about that case by the New York Times, the new chief of ICE, John Morton, issued a directive for field offices to make sure that other deaths had not been overlooked, a spokesman said.

David Shapiro, staff lawyer with the ACLU National Prison Project, said: “;Today's announcement is a tragic confirmation of our worst fears. Our nation's immigration detention system has been plagued by a total lack of transparency and accountability, and even with today's announcement there is no way we can be fully confident that there are not still more deaths that somehow have gone unaccounted for.”;

Few details of the newly disclosed deaths were provided, but other than Rodriguez and Negusse, all who died were Cuban nationals whose deaths occurred from 2004 to 2006.

Negusse died at Tallahassee Memorial Hospital, officials said, after he was removed from life support on the recommendation of a medical proxy.

The existence of undisclosed detention fatalities first came to light this spring, when the Times reported the case of Tanveer Ahmad, 43, a Pakistani New Yorker who had been held in a New Jersey immigration jail where a fellow detainee said that Ahmad's symptoms of a heart attack had gone untreated until too late.

The difficulty of confirming Ahmad's very existence showed that deaths could fall between the cracks in immigration detention, the hundreds of county jails, for-profit prisons and federal detention centers where about 400,000 people a year are held while the government tries to deport them. Ahmad turned out to be a longtime New York cabby who had overstayed a visa.

In April, an agency spokeswoman, Kelly Nantel, acknowledged that Ahmad's death had been overlooked, but added, “;We believe we have accounted for every single detainee death.”;

Yet in records turned over to the ACLU in late July, lawyers for the group said they were surprised to find yet another death that was not on the list obtained by The Times under the Freedom of Information Act and published last year on its Web site.

Previously, the only public documentation of such deaths had been pieced together by relatives of the dead and their advocates; as recently as 2007, they were aware of about 20 cases. Eventually ICE revealed that there had been 62 detention deaths since 2004 but declined to provide names, dates, locations or causes until compelled to do so under the Freedom of Information Act.

This month, the Obama administration announced a plan to revamp the detention system.