Washington, D.C. ? The Transportation Security Administration has lost a computer hard drive containing Social Security numbers, bank data and payroll information for about 100,000 employees.

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.

TSA said it has asked the FBI and Secret Service to investigate and said it would fire anyone discovered to have violated the agency’s data-protection policies.