Fifty-six people from 27 Monroeville homes were permitted to return to their residences after they were forced to evacuate last night because of a gasoline leak at the Sunoco station at Alpine Village Drive and William Penn Highway.

Hotel rooms had been made available to evacuees.

The source of the leak, which was reported at 4:30 p.m. Monday, was identified as one of two underground tanks at the gas station. A grassy stretch near the station was saturated with fuel, and gasoline fumes filled the air nearby. Both tanks were being emptied for inspection.

Sunoco hired a contractor to clean up the spilled fuel, Monroeville police said.

The Pennsylvania Fish and Boat Commission said a "significant" amount of the spilled or leaking gasoline -- more than 100 gallons -- found its way into nearby streams and caused the deaths of more than 200 fish.

The fish, mostly catfish and suckers, along with crayfish, were found along more than half a mile of Thompson Run, which flows into Abers Creek, a tributary of Turtle Creek.

No trout, which are stocked in Turtle Creek, were reported killed, said Emil Svetahor, the fish commission's southwest regional manager.

Mr. Svetahor said cleanup crews are working on the creeks and the commission could issue violation notices and fines to cover restitution for the loss of aquatic life.

Helen Humphreys, a state Department of Environmental Protection spokeswoman, said it's still not clear if the incident was caused by a leaking underground tank at the gasoline station or an "overfill" of the tank. She said the station does not have a history of pollution violations.

Mayor Gregory Erosenko said air testing in nearby homes was done as a precaution.

Evacuations were ordered on part of Alpine Village Drive and Matterhorn Road.

Those who evacuated were housed at the Red Roof Inn and a nearby senior citizens center. People with safety concerns were urged to call Monroeville police dispatch at 412-856-1111.

The evacuation order was lifted at 1 a.m. today after electric service was reconnected by Duquesne Light Co.

Equitable Gas Co., was to restore natural gas service this morning, after lines had been disconnected because of the leak, police said.