Media playback is unsupported on your device Media caption Dozens of emergency workers rushed to the scene

Six people have died and at least 14 have been hurt after a building collapsed in the centre of the US city of Philadelphia, officials say.

A four-storey building fell down, sending debris on to a building housing a bustling Salvation Army shop.

The collapse happened around 10:30 local time (14:30 GMT) in the Center City neighbourhood.

The building was being demolished, though the cause of the collapse was unknown, officials said.

Early reports said just one person had died, but rescuers continued working into the night.

Mayor Michael Nutter said the dead included five women and one man.

"If anyone else is in that building, they will find them,'' he said.

Thirteen people were taken to hospital suffering minor injuries, Fire Commissioner Lloyd Ayers said.

Late on Wednesday, a 61-year-old woman was pulled alive from the rubble to become the 14th known survivor.

'Lucky ones'

The four-storey building had both commercial and residential spaces.

Several witnesses said they had been concerned about the way the demolition was being carried out prior to the collapse.

"We've been calling it for the past week - it's going to fall, it's going to fall,'' window washer Dan Gillis told the Associated Press.

Image caption One person was pulled from the rubble in the early afternoon

Earlier, witnesses said they had heard a loud rumbling sound immediately beforehand.

"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," Veronica Haynes, who was in an apartment building nearby, said.

"Then you saw the whole side of the wall fall down... on to the other building.''

Bernie Ditomo told a local NBC broadcaster he was driving on a nearby street when he felt something "like an earthquake".

"I said, 'What the hell is going on?'," Mr Ditomo said. "My truck is totalled. I am a little dusty and dirty, but I'm alright. I am one of the lucky ones."

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

Authorities asked news helicopters to clear the air over the scene so rescuers could hear people trapped under the rubble.

"This is delicate, it is dangerous work," Mr Ayers said.