On Wednesday morning, a four-story building in Philadelphia collapsed unexpectedly, trapping some people under the rubble and injuring others.

As of noon, rescue workers are digging through the destruction in hopes of finding at least two people who are still missing. Twelve others have already been found and taken to local hospitals. None of them suffered serious harm, according to authorities.

The four-story structure was located at 22nd Street and Market Street in Center City, next to a Salvation Army thrift store that was also badly damaged in the incident. Construction crews had been working on a nearby building, which may have been part of what led to the collapse. At this point, the reason for the collapse is being called an industrial accident.

As search-and-rescue operations continue, all nearby streets have been closed down. Live coverage from NBC Philadelphia can be seen below:

We will continue to update this post as new information comes in.

[NBC]