Emergency personnel respond to a building collapse in downtown Philadelphia, where the city fire commissioner says as many as eight to 10 people are believed trapped in the rubble, Wednesday, June 5, 2013. (Dino Hazell/AP Photo)

Building Collapses in Philadelphia: 12 Injured, 2 Trapped

Philadelphia Mayor Michael Nutter calls the rescue effort 'delicate' and 'dangerous' work.

Emergency personnel respond to a building collapse in downtown Philadelphia, where the city fire commissioner says as many as eight to 10 people are believed trapped in the rubble, Wednesday, June 5, 2013. (Dino Hazell/AP Photo)
By + More

A four-story building in downtown Philadelphia collapsed Wednesday, injuring at least 12 people and trapping two others.

It's not immediately clear what caused the building, located at 2140 Market Street, to collapse. The collapse damaged two adjacent buildings, and at least some of the victims were inside a Salvation Army thrift store located at the intersection of 22nd and Market Streets.

[PHOTOS: Building Collapses in Philadelphia, Traps Victims]

"What we actually have is a four-story property that collapsed onto a two-story building," Philadelphia Fire Commissioner Lloyd Ayers said at a press conference shortly after noon.

Ayers said rescue personnel communicated with one person trapped beneath the debris and were working to remove the two people buried beneath rubble. "We are in the process of extricating these people," he said.

Around 125 rescue personnel were working the scene, Ayers said.

An official with the city's permitting commission said that the four-story building's owners acquired a demolition permit in February. "The permits were valid and up-to-date," the official told reporters, and there were no known violations.

This photo was purportedly taken by Flickr user Luidude moments before the collapse:

Philadelphia Mayor Michael Nutter joined Ayers at the press conference.

"I come through here a million times," Nutter said. "At any point in time, you're not necessarily going to know how many people were in this [thrift] store."

Nutter described the rescue operation as "delicate" and "dangerous" work. He asked city residents to respect a perimeter established around the scene.

WPVI-TV reports that the building collapsed at approximately 10:45 a.m. EDT. "Bystanders immediately jumped into action, helping first responders to locate and assist the wounded," the station reported.

The building went down with a boom. One witness told the Philadelphia Inquirer they heard what sounded like a "freight train."

Yahoo! Sports writer Les Carpenter reported on Twitter that police dogs were on the scene to assist with recovery efforts. A photo tweeted by Carpenter showed a cloud of dust rising from where the building collapsed.

More News: