Eight people have been confirmed dead and 14 are seriously injured in hospital after a police helicopter crashed into a busy pub in Glasgow city centre.

Air accident investigators were examining the wreckage of the helicopter on Saturday to discover why it lost power and plummeted into the Clutha Vaults pub on Stockwell Street, a short distance north of the river Clyde, on Friday night.

Sir Stephen House, the chief constable of Police Scotland, confirmed the deaths on Saturday afternoon.

Alex Salmond, Scotland's first minister, said: "This is a black day for Glasgow and for Scotland. Our condolences go to those who will be bereaved, our solidarity with those who have been injured.

"But it's also St Andrew's Day and it's a day we can take pride and courage in how we respond to adversity and tragedy, and the response from our emergency services and ordinary citizens has been exemplary."

The Eurocopter EC135 T2 was piloted by a civilian and was carrying two police officers when it crashed at 10.25pm. It landed on the Clutha Vaults pub, where more than 100 people were listening to a folk-ska band called Esperanza who were playing as the roof collapsed.

Emergency services work on the roof of the Clutha Vaults pub. Photograph: Jeff J Mitchell/Getty Images

Jim Murphy, the Labour MP for East Renfrewshire, was in a nearby pub and rushed to help.

"People reacted the right way, almost like a human chain, mostly men standing in line, passing injured people from one to another to get them out, drag folk from the debris to get them out," he said.

"I have no idea how many. I helped only bring out about four people. There was a lot of walking wounded, a lot of people with cuts and bruises. As you got to the front door of the pub there was just debris, you were just trying to get people out. There was a mixture of injuries, I'm not a doctor – two women in particular were unconscious and we were getting them dragged out."

Thirty-two people were taken to Glasgow Royal Infirmary, Victoria Infirmary and the Western Infirmary. Firefighters appeared to have stopped searching the site by Saturday afternoon.

Outside the crash site, John McGarrigle, 38, was waiting for information about his father, also called John, who was a regular at the Clutha.

"As soon as I heard what had happened I just knew that my dad was dead," he said. "They haven't confirmed that yet, but he's a regular and it came through right at his usual spot. I just know he's dead.

"He had friends with him. One of them stepped outside just before it hit, the other went to the toilet. That's what saved them. I would have been there sitting right next to him if I hadn't met my girlfriend earlier in the night.

"I've been trying all night to get news. My sister went to his house and he wasn't there. We've been to all the hospitals and he wasn't there."

William Byrne, 48, from Coatbridge, said the band continued to play after the first impact and then the roof collapsed.

"The gantry of the bar and parts of the roof came down. My brother and I lifted it up because there were people trapped under. Then we held the doors open while people filed out. It was only 15 minutes later when the police told us it had been a helicopter.

"But we had no idea there was a helicopter in the bar and I don't know whether anybody was able to help the people inside it."

Map showing the location of the Clutha Vaults bar. Photograph: Finbarr Sheehy for the Guardian

Police cordoned off the area, a short distance from Glasgow's main shopping streets. Struan Johnston, of the aviation consultancy Caledonian Aviation, said that judging from the evidence he could see, the helicopter's pilot had possibly made a controlled landing on the roof which had then collapsed under the weight of the aircraft.

"What I suspect given what we're hearing from various eyewitnesses is that it was a relatively controlled descent, but these helicopters operate at such low level that with any problem, the pilot would have a very, very short time to make any decision.

"Given he's so close to King Street car park, I wouldn't be surprised if he had made to get there but the tall buildings [around the car park] prevented him from getting there."

He said the aircraft has a form of rubber bladder within the fuel tanks to help prevent an explosion in a crash, which may explain why there was no explosion when it hit the pub roof.

Crowds at Scottish Cup football matches observed a minute's silence for the victims of the crash and Scottish flags were lowered to half-mast across the country.

David Cameron, the prime minister, said: "This is a tragic event and our deepest sympathies are with the families and friends who lost a loved one last night.

"I want to thank the emergency services who worked tirelessly throughout the night and I also want to pay tribute to the bravery of the ordinary Glaswegians who rushed to help."