Maryland Congressman Elijah Cummings is asking the nation's Postmaster General to explain how hackers were able to steal sensitive data on Postal Service employees.
The U.S. Postal Service said Monday it is the victim of a cyberattack and that information about its employees, including Social Security numbers, may have been compromised.
The FBI and other federal agencies are investigating, the agency said in a statement.
Postal Service spokesman David Partenheimer said the personal information that may have been obtained in the attack includes employees' names, dates of birth, Social Security numbers, addresses, emergency contacts and other information.