Nine people have been taken to hospital after a tour bus carrying American punk rock band Baroness plunged over a viaduct in heavy rain.
The band, who come from Savannah, Georgia, were touring Britain and Europe when their coach ploughed through a safety barrier and fell 30ft.
The emergency services said two people, including the driver, were trapped in the wreckage.
They were cut free and, having suffered the "most serious injuries", including multiple fractures, were taken to Frenchay Hospital in Bristol.
According to Great Western Ambulance Service, the other seven, who suffered "more minor injuries", were taken to the Royal United Hospital in Bath.
Baroness, whose line-up consists of John Baizley, Peter Adams, Matt Maggioni and Allen Blickle, played in Bristol on Tuesday night.
They were travelling to a gig in Southampton when the incident happened at the junction of Brassknocker Hill and the A36 in Bath at 11.30am.
A spokesman for the band said: "Baroness have been involved in a motor coach accident in the Bath area of England.
"All band members and personnel on board are currently receiving medical treatment.
"The band had performed in Bristol last night and were travelling to Southampton for a performance at Talking Heads this evening.
"All remaining dates on the band's European tour have been cancelled."
Eyewitnesses said they heard a loud bang and rushed to the scene.
Site manager Tony Cook, 61, was one of the first people to arrive as he was working at a property at the bottom of Brassknocker Hill.
Mr Cook said when he and some of the other workmen got to the coach they found the driver hanging out of the front window.
After helping him out, he told them there had been a problem with the steering.
"At the top of the hill it is quite windy so they were going quite slow and seemed to be taking it quite carefully," Mr Cook said.
"It was torrential rain - it was like one of these eastern storms or something, it was like a river down here.
"Whether the brakes went at the bottom or, what the driver said to one of my blokes, was that the steering went, he couldn't get around the coroner, so whether the hydraulics or something went, I don't know.
"When we got down there the driver was hanging out of front of the coach, but his legs were trapped so we had to free him and get him back and comfortable.
"Then we got some ladders down there so that the people that were conscious inside could get out.
"We just got the people to the side of the road and made them comfortable and just helped where we could because obviously there was quite a bit of commotion, screaming and that, but then the police and the ambulance got here and they took over.
"It was a left-hand drive, German coach, and inside there were all fairy lights, but it was all quite a mess by the time we got there.
"First of all you think maybe his brakes went, but I don't think he would have got quite as far around, but he said he couldn't steer around the corner, so it could have been that he was going too fast, but it could be a combination of things."
No other vehicles were involved in the crash with the single-decker black and red German coach.
It appeared the vehicle had failed to stop at the bottom of the T-junction at Brassknocker Hill and crashed over the viaduct.
An Avon Fire and Rescue spokesman said: "For reasons that are not yet known, the coach failed to stop at the bottom of Brassknocker Hill, travelled across the A36 and left the road, dropping around 30ft below, coming to rest near a canal."
The coach came to a standstill with its wheels still on the ground, taking with it foliage and tree branches which now cover the roof of the vehicle.
Coach seats and bits of wood from inside had been pulled out and all of its windows were smashed.
Inspector Steve Mildren, from Avon and Somerset Police, told reporters at the scene: "At 11.30am this morning we received a telephone call from a member of the public.
"They told us a coach had come down over Brassknocker Hill at the junction of the A36 and had left the road and had landed on the road at the bottom of the viaduct.
"We know that there were nine passengers on the coach.They have all been accounted for and there are some injuries there and they are receiving medical treatment at hospital.
"At this time we don't believe that any of those injuries are life-threatening.
"It had been raining really heavily, as it has been for much of the day."
He added that an investigation was now under way to establish how and why the coach left the road.