PHILADELPHIA—Philadelphia's gas utility says it is working to repair a gas main where a leak disrupted mass transit service in the city and suburbs and forced scores of evacuations.

A Philadelphia Gas Works spokesman says crews found the leak in a 4-inch main that feeds a maintenance building at the Fern Rock Transportation Center in north Philadelphia.

Officials said the problem was first reported around 9 a.m. Wednesday. Fire officials said about 175 people were evacuated from area homes as a precaution, but the utility said Wednesday afternoon that all had been allowed to return. No injuries were reported.

The Southeastern Pennsylvania Transportation Authority said normal operations had resumed by 1 p.m. Wednesday, but warned that there might be residual delays.