PHILADELPHIA — A four-story building that was being demolished collapsed onto an adjacent thrift store in central Philadelphia on Wednesday morning, killing at least six people, city officials said.

One wall of the building collapsed about 10:45 a.m. during demolition work, sending bricks and other debris thundering into the Salvation Army store. Mayor Michael A. Nutter confirmed at a news conference late Wednesday that five women and one man, all found in the rubble of the thrift store, had died. He gave no further details about the deaths, and said a search was continuing.

One person was pulled out alive after being trapped for more than 12 hours, said Mark McDonald, a spokesman for Mr. Nutter. The survivor was taken to a hospital, but Mr. McDonald provided no more details.

Image Credit... The New York Times

Thirteen others escaped with only minor injuries, officials said.

The cause of the collapse, which occurred on Market Street near 22nd Street, was not immediately known. Several government agencies, including the federal Occupational Safety and Health Administration, will investigate.