Emergency officials scrambled for hours yesterday in Delaware County to locate the source of an underground gasoline leak that forced evacuations in Aston Township and triggered fears of an environmental catastrophe.

The leak was detected about 9 p.m. Tuesday when a Clearview Lane resident reported a strong gas odor, which was later detected in neighboring homes. The gas apparently had entered the township sewer lines.

Firefighters from Delaware and Chester counties and New Castle, Del. converged on Aston, along with officials from the U.S. Environmental Protection Agency and state Department of Environmental Protection.

About 4 p.m. yesterday, diggers located the source of the leak inside a tank farm on Cherry Tree Road near Frazer Lane, according to Sean Joyce, Aston's assistant fire marshal.

"We're just excited that at this point we feel like we can contain it," Joyce said, after emergency officials met inside a mobile command center near the dig site. "Once we contain it, we can fix it."

Last night, the source was believed to be a pipeline owned by either ConocoPhillips or Buckeye Partners. Cold weather may have caused the pipe to burst.

DEP and EPA officials were on the scene, but Joyce said that the preliminary findings showed that the leak was not large enough to pose a widespread environmental threat.

Delaware County Emergency Services Director Ed Truitt said that pinpointing the source was difficult because 34 pipelines run through the county, carrying gasoline, heating oil and jet fuel from as far away as Port Arthur, Texas.

"You can't imagine how much product is in a pipeline per mile," Truitt said.

At least four Aston homes were evacuated. No injuries were reported.

"It's just been a long night," Joyce said. "The whole county has literally supplied manpower for this operation."

Yesterday's leak was not the first time Aston residents have dealt with ruptured pipes.

Homes on Edgar Avenue have repeatedly been flooded by overwhelmed sewer lines during heavy rain.