A building collapse in Philadelphia Wednesday has many people scratching their heads as to what caused the accident. Rescue workers continue to sift through the rubble in an attempt to save as many as they can.

So far one person is confirmed dead and 14 others are injured as authorities continue rescue efforts this afternoon. It is unknown how many people were in the building at the time and therefore hard to say just how many potential deaths and injuries there are.

"I was parked on 21st just heading to Market Street, next thing you know it felt like an earthquake," said Bernie Ditomo, a truck driver with Belfi Brothers. "I said, 'What the hell is going on?' My truck is totaled. I am a little dusty and dirty, but I'm alright. I am one of the lucky ones."

The collapse of a four-story building's outer wall rained brick and mortar down upon an adjoining two story building that housed a Salvation Army. It was in that Salvation Army that those who were killed and injured were located.

"Let's again keep in mind that we did not know and do not know how many people were actually in the thrift store," Mayor Michael Nutter said this afternoon. "That is why the fire department search and rescue operation continues."

The four-story building that partially collapsed was an abandoned structure that was undergoing demolition efforts. It is uncertain exactly what caused the collapse, though an investigation is already under way in the matter.

"There was a big aftershock," said witness Jordan McLaughlin. "There were people that fell over, there were people screaming and running across the street. We could hear people screaming inside the building."

As soon as the building collapsed, people immediately rushed to help those trapped under the rubble. Nearby roofers dropped what they were doing to assist until rescue workers came. Now, there are over one hundred workers helping at any one time from both the police and fire departments as well as other organizations.

"We're getting fresh personnel and staffing here to dig and we've had two dogs to come out and work the pile to locate others so we know exactly where to dig," Fire Commissioner Lloyd Ayers said at a press conference.

The rescue efforts have been so tiring that the workers are being constantly rotated out and even the dogs have been replaced with fresh noses. Though the collapse is not believed to be an act of terrorism, the city's counter-terrorism task force is also on the scene along with all the major utility companies.