Investigators, meanwhile, tried to determine what caused a four-story building that was being demolished to collapse onto a neighboring Salvation Army Thrift Store at 10:45 a.m. EDT (1445 GMT) on Wednesday, burying shoppers in concrete and debris.
In a round-the-clock search, rotating fire companies picked through the heaps of concrete chunks and splintered wood at the scene on Philadelphia's busy Market Street, partially blocked off since the disaster, a spokeswoman for the Philadelphia Fire Department said on Thursday.