Authorities realized Thursday the hard drive was missing from a controlled area at TSA headquarters. TSA Administrator Kip Hawley sent a letter to employees Friday apologizing for the lost data and promising to pay for one year of credit monitoring services.
"TSA has no evidence that an unauthorized individual is using your personal information, but we bring this incident to your attention so that you can be alert to signs of any possible misuse of your identity," Hawley wrote in the letter, which was obtained by The Associated Press. "We profoundly apologize for any inconvenience and concern that this incident has caused you."
The agency said it did not know whether the device is still within headquarters or was stolen," the agency said in a statement Friday.
The hard drive contained information on employees who worked for the Homeland Security agency from January 2002 until August 2005.
TSA, a division of the Homeland Security Department, employs about 50,000 people and is responsible for security of the nation's transportation systems, including airports and train stations.
It is the latest mishap for the government involving computer data. Last year, a laptop with information for more than 26.5 million military personnel, was stolen from a Veterans Affairs Department employee's home. Law enforcement officials recovered the laptop, and the FBI said Social Security numbers and other personal data had not been copied.