By David Shepardson

WASHINGTON The personal information of 237,000 current and former federal government employees has been exposed in a data breach at the U.S. Transportation Department (USDOT), sources briefed on the matter said on Friday.

The breach hit systems for processing TRANServe transit benefits that reimburse government employees for some commuting costs. 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, it said.

The maximum benefit allowance is $280 per month for federal employee mass transit commuting costs.

(Reporting by David Shepardson; Editing by Chris Reese and Cynthia Osterman)