Three people have been killed after a police helicopter crashed into a crowded pub in the Scottish city of Glasgow, the BBC has reported.

The broadcaster cited a source close to the investigation as saying that the death toll would almost certainly be higher.

Scotland Police said on Saturday that 32 people were evacuated to hospitals across Glasgow and rescuers were searching through the ruins of the pub where the helicopter carrying two police officers and a civilian pilot crashed.

Witnesses said there were about 120 people inside The Clutha pub when the accident occurred.

“A full investigation is now under way however at this early stage it is too early to provide details on why the helicopter came down,” said deputy chief constable Rose Fitzpatrick.

“We are working hard to recover people still inside the building and we will make further details available when we have them,” she added.

Witnesses told British media that the helicopter came down on the pub “like a stone.”

Alex Salmond, Scotland’s first minister, said human casualties were likely.

“Given an incident of this scale we must all prepare ourselves for the likelihood of fatalities,” Salmond said on Twitter.

Guests were listening to a band at the time of the crash.

“They carried on playing and then it (the roof) started to come down more and someone started screaming and then the whole pub just filled with dust,” Grace MacLean, who was in the pub, told BBC. “You couldn’t see anything, you couldn’t breathe.”

“People started coming out with injuries and blood and everyone was going over and trying to help out. I don’t think it crashed, if it had crashed there would have been fire, there would have been a noise, but we didn’t hear anything, it was the smoke that we noticed.

“I think maybe whoever was in the helicopter just tried to land on the roof or something.”