U.S. Transportation Department (USDOT) has faced a cyber attack exposing the personal information of 237,000 current and former federal government employees.
It was not clear if any of the personal information had been used for criminal purposes.
USDOT said in a statement to Reuters that the breach did not affect any transportation safety systems. It did not say who might be responsible for the hack.
The department is investigating the breach and has frozen access to the transit benefit system until it has been secured and restored.