Silence has long shrouded the men and women who die in the nation’s immigration jails. For years, they went uncounted and unnamed in the public record. Even in 2008, when The New York Times obtained and published a federal government list of such deaths, few facts were available about who these people were and how they died.

But behind the scenes, it is now clear, the deaths had already generated thousands of pages of government documents, including scathing investigative reports that were kept under wraps, and a trail of confidential memos and BlackBerry messages that show officials working to stymie outside inquiry.

The documents, obtained over recent months by The Times and the American Civil Liberties Union under the Freedom of Information Act, concern most of the 107 deaths in detention counted by Immigration and Customs Enforcement since October 2003, after the agency was created within the Department of Homeland Security.

The Obama administration has vowed to overhaul immigration detention, a haphazard network of privately run jails, federal centers and county cells where the government holds noncitizens while it tries to deport them.