The driver of a coach involved in a crash that left three people dead and 50 others injured probably had a heart attack at the wheel, his boss has said.
David Hannell, the owner of Merseypride Travel, told Sky News that a scenario in which 63-year-old Colin Daulby suddenly collapsed at the wheel was the "only way we can assess what happened".
He added: "(A heart attack) is the only thing we can think of. We don't think he fell asleep because he had only just started off."
Mr Daulby, from Merseyside, was among the three people killed when the coach he was driving, which had only been on the road for around an hour after leaving Portsmouth, overturned on its way back from the Bestival music event.
The vehicle was returning to Merseyside from the festival on the Isle of Wight when it careered off the road and hit a tree on the A3 near Hindhead, Surrey, just before midnight on Monday.
Michael Molloy, an 18-year-old festivalgoer from Woolton in south Liverpool, was also killed.
He was a talented local musician and a member of the aspiring Liverpool-based band Hostile Radio. On the group's Facebook page Andy Paton wrote: "RIP Mike just can't believe it. So much talent, and a great lad."
The third victim, understood to be a woman, is yet to be named by police but relatives have been notified.
All 50 survivors, mostly aged between 18 and 25, were taken to hospital, many of them with 'life-changing' injuries, including lost limbs. Some 11 people remain in hospitals across the south east.
Police are trying to establish whether the coach may have been overloaded, as despite 53 people being on board, the vehicle only had 51 passenger seats.
No other vehicles were involved and police said neither the road conditions nor the weather was thought to be a factor.
A Surrey Police spokeswoman told Sky News: "A collision investigation will be a thorough investigation into the circumstances surrounding the incident.”
Mr Hannell denied "overloading" was a factor - pointing out that one crew seat, one driver seat and 51 passenger seats added up to 53.
The vehicle has been described as a 51-seat 'exec coach' which was 16 years old.
He said an account from a woman who witnessed the smash added to his speculation that Mr Daulby had suddenly fallen ill with a heart attack.
He told Sky News: "I've just spoken to a lady who was travelling in a car with her partner behind the coach at about 50mph. She just told me the coach was being driven very carefully but he did not take the bend and just went straight on without braking.
"The lady said (the coach) was not being driven erratically. It was being driven perfectly."
He added that the driver did not have any known medical problems.
"He was fit as a fiddle. He wasn't overweight and went walking," he said.
Citing the Bolton Wanderers player Fabrice Muamba, who collapsed with a heart attack in the middle of a football match earlier this year, he added: "People have heart attacks when they are perfectly fit."
Tributes have been paid to Mr Daulby, who was described by his neighbours in Warrington as an "all-round good guy".
Tom McLoughlin said: "We're all in shock. This is a close-knit street and everyone knew Colin.
"I had known him for 20-odd years and spoke to him only the other day."
Chris McGee, a DJ at Liverpool radio station Juice FM, is among those believed to be seriously injured.
Bestival organisers said in a statement: "This is devastating news. Our thoughts are with the relatives of those affected by this tragic incident."