Social Security numbers and other personal information for as many as 2.2 million US military personnel -- including nearly 80 percent of the active-duty force -- were among a large batch of data stolen last month, The Washington Post reported on Wednesday.
Personal data for as many as 1.1 million active-duty military personnel, 430,000 National Guard members and 645,000 reserve members may have been included on an electronic file stolen on May 3 from an employee's home of the Veterans Affairs Department, officials were quoted as saying.
The data include names, birth dates and Social Security numbers of the military personnel.
The loss is unprecedented and raises concerns about the safety of US military forces, defense officials said.
But they cautioned that law enforcement agencies investigating the incident have not found evidence that the stolen information has been used to commit identity theft.
The information could be used to find out where military personnel live, and could potentially put military personnel and their families at jeopardy of being targeted, security experts said.
The revelations significantly increase the risk of potential harm in what was already one of the largest data breaches in US history, the report said.
On May 22, the Veterans Affairs Department disclosed that an external computer hard drive had been stolen on May 3 from the home of a VA analyst in Montgomery County, Maryland, and that it contained unencrypted names and birth dates of as many as 26.5 million veterans who were discharged after 1975 or who had submitted benefit claims.
Initially the department thought that all of the 26.5 million people affected were veterans, but a database comparison revealed that they also included the bulk of active-duty military services, as well as more than 1 million members of the National Guard and reserves.
Montgomery County Police released a description on Tuesday of the stolen laptop and its external hard drive and offered a 50,000-US dollar reward for information leading to the recovery the laptop.
The analyst, 60, who was not identified, has been fired. His boss resigned last week, and another senior official of the department was on administrative leave pending investigations, the report said.
Meanwhile, a coalition of veterans groups have filed a class-action lawsuit against the federal government on Tuesday, contending that privacy rights had been violated and seeking 1,000 US dollars in damages for each affected veteran.