A man suffered a broken jaw and another was taken to hospital when a stunt at an extreme motorsports show went wrong.
The Nitro Circus at Glasgow's SSE Hydro was temporarily halted on Thursday night after the failed attempt to perform a backflip off a ramp.
The three passengers on the bike with a stunt driver had been thought to be audience members but the BBC reported they were actually part of the act.
The bike appeared to stall near the top of the ramp and tipped over the side.
The rider and one of the passengers were able to walk away but two others were treated by medics at the scene before being taken to hospital.
Nitro Circus said one man broke his jaw in the fall while the other is fine "apart from some bruises". All of those taking part were wearing helmets.
The BBC reported that although they were announced as audience members, they were actually stuntmen, a claim Nitro Circus has yet to comment on.
The father of a boy who took part in a botched bike stunt said the crowd went silent as the bike 'fell back.'
The dad, who has not been named, said: "They went forward towards the ramp, not too fast, and hit the bottom of the ramp and the speed died.
"They got to the top of the ramp and just stopped. The crowd went completely silent, they knew something was wrong. They lost their balance and fell. One fell backwards and rolled down the ramp. The other three fell down the left hand side."
He said his son, who is not believed to be seriously injured, put his hand up when the team appealed for volunteers.
"He now wishes he hadn't," he added.
He said he followed the team online and was aware accidents like that could happen.
He said: "They've put videos up before. This trick was tried eight times in America and all eight times it failed."
A spokesman for Nitro Circus said: "During Thursday night's Nitro Circus Live show at Glasgow's SSE Hydro Arena, two passengers who sustained injuries during a four-person motorbike backflip attempt were transported to a nearby hospital.
"One is fine apart from some bruises. The other has a broken jaw and will have surgery on Friday, but is in good spirits and is expected to make a full recovery.
"Nitro Circus considers health and safety its top priority, and has expert medical staff on site in the event of an emergency."
Video posted on social media showed the incident and the MC of the event told the audience: "That is the worst crash we have ever had".
The show was paused while workers and medical staff rushed to the scene and the MC added: "It's obviously not planned - occasionally something can go wrong. It's not meant to go wrong, so we're taking a moment."
Nitro Circus, which describes itself as an action sports entertainment company, is currently touring across Europe.
The event is being staged at London's O2 on Saturday and Sunday before moving to Zurich and Paris.
One fan at the Glasgow show tweeted: ''Just at Nitro Circus in Glasgow. Hope the chaps on the four person backflip are ok! stretchered keep us updated!''
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