UPDATED: The U.S. Geological Survey now says it was an earthquake, after all, that shook homes in Philadelphia's Far Northeast - near Knights and Fairdale roads - last night.
Shortly before 10 p.m., hundreds of wide-eyed Northeast Philadelphia residents were driven from their homes by an unknown, unseen force that briefly shook the ground beneath their feet.
Cops, firefighters, medics and other emergency responders swarmed the neighborhood just east of Northeast Philadelphia Airport after numerous people reported feeling their houses shake from what seemed to be some sort of explosion. Residents in lower Bucks County reported the same thing.
The cause of the boom was a mystery last night. Emergency crews found no fires, no explosions, no signs of damaged homes or injured residents.
Peco Energy spokesman Ben Armstrong said the company had no reports of power outages.
"We had a crew respond and inspect our equipment in the area," he said. "At this point, we don't believe it's anything Peco-related. We don't know what's going on."
Similarly, a police official said the Water Department had received no reports of lost water pressure that would have indicated that a pipe had burst. Police helicopters hovering over the area saw no evidence that anything ominous had occurred.
And last night, the U.S. Geological Survey reportedly said that there was no evidence that an earthquake - or even a small tremor - had occurred. But Saturday, the survey changed its response.
The Fire Department officially declared the situation under control about 10:45 p.m.
Alex Baez, who lives near the Franklin Mills Mall, said he felt the disturbance miles from Knights and Fairdale roads, where police, fire and utility crews converged.
"The whole building shook," he said about 11 p.m., adding that he was reluctant to return home until someone figured out what had happened.
Baez said he felt a major rumble, then a smaller one that shook his TV.
"I want safety, man!" he said, laughing.
Edward Turzanski was at a nearby school when, he said, "there was a loud bang, then a sharp jolt from below."
About 11:30 p.m., emergency crews began leaving Knights Road and allowing regular traffic to travel through the area.
"I thought it was an earthquake; I felt it twice," said Matthew Patton, who lives on nearby Whiting Road. "The second one was smaller, though."
Patton's sister, Jennifer, said she was at a neighbor's house and initially thought someone inside had fallen.
She joked that the Rapture - which Christian evangelist Harold Camping had predicted would occur last Saturday - was getting started a few days late.
Just before midnight, motorists on Knights Road pulled over and asked neighbors if anyone knew what had happened.
Their questions were met with quiet shrugs.