Philadelphia officials are trying to figure out what caused thousands of cockroaches to emerge from a manhole this weekend and swarm a neighborhood.
A resident of the Bridesburg neighborhood told WCAU-TV the bugs emerged Sunday night, and have been invading the area ever since.
"When I tell you thousands of them, there were thousands of them," Pat Wall told WCAU-TV.
Wall said the sea of bugs was so thick that residents couldn't see the ground, describing it as "a horror story."
Another resident told the television station the infestation has spurred neighbors to venture outside with spray cans and go after the critters.
"They were stomping them and they were running right out of there," Paul Basfort said.
Water department spokesman John DiGiulio said crews will be out Tuesday investigating. DiGiulio said a sewer inlet might be clogged with food and trash that can attract the bugs, which are also known to multiply in warmer weather.
The Associated Press contributed to this report.