(Reuters) - Residents of a Philadelphia street were horrified when thousands of cockroaches emerged from a sewer drain, forming a swarm so big that it covered the street at one stage, according to city officials and local media on Tuesday.

“There were thousands of them,” resident Pat Wall told NBC10 television of the Sunday-night incident. “It was a horror story that I couldn’t believe I was living.”

A small task force of city workers on Tuesday found the source of the infestation, a drain clogged with refuse, said John DiGiulio, a spokesman for the Philadelphia Water Department. That may have contributed to the swarming in the city’s riverfront Bridesburg neighborhood, he said.

Roaches are a fact of life all over the city, and the creatures thrive in warm, moist environments, DiGiulio said.

“It’s unfortunate but they do live in those type of environments,” he said. “It could have been a disturbance or anything to make them come out.”

Sewers are normally cleaned out every few months by the water department and more frequently when a complaint is received, according to DiGiulio.

Health department workers will also bait the sewer line in an effort to fight the bugs.