The US Federal Aviation Administration disclosed Monday that the personal data of more than 45,000 employees and retirees was stolen after hackers broke into a computer server at the agency.

Two of the 48 files on the server contained personal data for people who were on the FAA's payroll during for the first week of February 2006, the agency said. Those affected will be notified by letter, and law enforcement authorities have been contacted, according to the FAA, which said that the data breach didn't affect air traffic control or other operational systems.

"The FAA is moving quickly to prevent any similar incidents and has identified immediate steps as well as longer-term measures to further protect personal information," the agency said in a statement.

FAA is the latest federal agency to be affected by a breach, either via a system intrusion or the loss or theft of laptop PCs containing unencrypted data.

In the most serious incident involving a government agency thus far, the Department of Veterans Affairs reported in May 2006 that a laptop and hard drive containing the personal information of 26.5 million military veterans and active-duty personnel had been stolen from an employee's home that month. The laptop and drive were recovered the following month, and VA officials said that the data on them appeared to have been untouched. But the incident sparked an overhaul of the VA's IT department and security changes across the government.

Jeremy Kirk of the IDG News Service contributed to this story.