One dead, 12 injured in Philadelphia building collapse

A FOUR-storey building being demolished collapsed in Philadelphia, killing one person, injuring 12 and leaving people trapped in the rubble.

One person was killed in the collapse, NBC10 reports, adding that 13 people have been rescued and at least one person remains trapped.

Emergency crews on are the scene and working to find and free survivors. Earlier, Philadelphia Fire Commissioner Lloyd Ayers said around eight to ten people were believed to be trapped in the rubble.

Mr Ayers said 11 people have minor injuries. At least five people were taken to local hospitals, officials said.

The collapse involved a four-story building that once housed a first-floor sandwich shop. It collapsed, sending tons of debris onto a Salvation Army coer thrift store next door. The two are adjacent to an adult bookstore and theatre that had been taken down earlier.

Witnesses said they heard a loud rumbling sound immediately before the collapse.

Veronica Haynes was on the fifth floor of an apartment building across the street.

The building collapse in central Philadelphia has left 12 people injured. Picture: AP Photo/Dino Hazell

"I was standing there looking out my window, watching the men at work on the building, and the next thing I know I heard something go kaboom," she said. "Then you saw the whole side of the wall fall down ... onto the other building."

Bill Roam, a 54-year-old construction worker who has been working on a remodelling project at a nearby site for several days, heard the collapse and ran over. He said the dust was so thick that it was hard to see, adding that he was conceed in recent days by the way the building was being demolished.

High school student Jordan McLaughlan said he saw several people on the ground being given oxygen by rescuers after the collapse.

"It was hard to breathe, there was a lot of dust everywhere," McLaughlan said.

The accident happened at 10:45am (12.30 AEST) Wednesday on the weste edge of downtown, between the city's business district and its main train station.

McLaughlin told local radio station KYW that he rushed to help after "a building collapsed the wrong way and landed on a thrift shop". He said he helped two people out of the rubble, and saw five more people escape within ten minutes, CNN reports.

Rescue workers search the scene of a building collapse in downtown Philadelphia. At least one person was killed in the collapse. Picture: AP Photo/Philadelphia Inquirer, Michael Bryant

There is no word on exactly what caused the collapse.