LONDON (AP) -- A helicopter slammed late Friday night into the roof of a popular pub in Glasgow, Scotland, apparently crashing inside the building and littering the roof with debris.

Photos of the scene aired on local television show what appear to be the helicopter's propeller sticking out of the top of the pub's roof. Nearby wreckage appears to have the word "police" across the side. Rescue workers swarmed the door of the pub and several fire trucks were on the scene.

Local police confirmed emergency services are dealing "with a major incident," but would not comment on casualties or if a police helicopter was involved.

There were reports that people may have been trapped inside, but they could not be immediately confirmed. Glasgow ska band Esperanza were due to play a show at the pub.

Witnesses described a chaotic scene as people rushed through a cloud of dust to get out, some with bad gashes to the head and other injuries. Others formed a human chain to pull people out of the damaged building, one witness said.

"The helicopter was inside the pub. It's a mess. I could only get a yard or two inside. I helped carry people out," Labour party spokesman Jim Murphy told Sky News. "I saw a pile of people clambering out of the pub in the dust. No smoke, no fire, just a huge amount of dust."

People formed a human chain to help pass unconscious people out of the pub so that "inch by inch, we could get the people out," he said.

Gordon Smart, editor of the Scottish edition of the Sun newspaper, told Sky News he believed it was a police helicopter.

"There was no fireball and I did not hear an explosion," he said. "It fell like a stone. The engine seemed to be spluttering."

Prime Minister David Cameron tweeted: "My thoughts are with everyone affected by the helicopter crash in Glasgow -- and the emergency services working tonight."