At least two rowhouses were damaged when one collapsed late this morning in the 6000 block of Spruce Street.
"Everyone was accounted for," and no injuries were initially reported, said Executive Fire Chief Peter Crespo.
The first floor of one home appeared crushed under the weight of a tilting second floor, with some damage to an adjacent residence.
Emergency personnel were dispatched at 11:52 and arrived at the scene at 11:56, Crespo said.
Crespo declined to rule out possible explanations, except to say no fire was involved.
"I’m not going to speculate," he said. "It’s under investigation, that’s all I can tell you.”
After checking whether any neighboring houses might also be unsafe, the Department of Licenses and Inspections is expected to determine what can be repaired and what might have to be demolished.
The fire marshal will be part of the investigation, Crespo said.
Contact staff writer Peter Mucha at 215-854-4342 or firstname.lastname@example.org.