Mystery surrounds the identity of the second victim of the M25 coach crash near Heathrow, police have said.
Fire crews had to cut passengers from the wreckage
Officers are unable to identify the man, but have said he is Oriental, in his mid-20s and between 5ft 6in and 5ft 8in tall.
The 40-year-old driver arrested after the National Express coach overturned on Wednesday has been released.
He was held on suspicion of causing death by dangerous driving and was freed on bail.
Twenty-three people remain in hospital, some of whom have lost limbs, following the crash on an M25 slip road.
The company has withdrawn all 12 of its double-decker Neoplan Skyliner vehicles as a precaution following the incident near Heathrow Airport in west London.
In a statement the Neoman Bus group said: "We believe there should be no concerns among passengers regarding their safety due to the technical performance of these vehicles."
The statement added that: "Neoplan double-deck-vehicles operating in the National Express fleet have been examined thoroughly overnight. As expected, all have passed these safety checks and are available for immediate return to service as and when the operator wishes."
Chris Toner, from Monifieth, was killed in the crash
All those on board the coach, 67 passengers and two drivers, were taken to hospital following the crash.
A man and a woman died. The woman was later named as Chris Toner, 76, from Monifieth, near Dundee.
A three-year-old boy and a baby girl are being treated at St Mary's Hospital in London after losing limbs.
The majority of people were treated at Hillingdon Hospital in west London, where two people remain in a critical condition and 10 are said to be serious.
James Lant told the BBC how his step-brother, 69-year-old Michael Milbourne, was returning to Scotland after spending Christmas and New Year with his family in London.
He said his step-brother told him how the coach was going on to the slip road on the M25 when it veered to the left then right and then went out of control.
"He was in a bad way. There were people distressed all around him and inside the coach people were on top of one another," said Mr Lant.
National Express said there was no suggestion of any stability problem with the coaches at this stage.
Paul Bunting, National Express chief executive, said: "As a precautionary measure, we felt it necessary to temporarily withdraw the fleet as soon as possible.
"We will ensure this process is thorough and comprehensive as part of our commitment to passenger safety."
The Neoplan Skyliner has, by law, been fitted with a speed limiter restricting it to 62mph.
And all double-decker vehicles undergo Department for Transport safety tests to show they can tilt 28 degrees with the top deck full and the bottom deck empty, without tipping over.
In 2003, 28 people died when a similar double-decker coach overturned in France.
Simon Posner, from the Confederation of Passenger Transport, said: "Coach travel is by far the safest way to travel on the roads today, every figure will show you that.
"Also, there is no evidence showing double-deck vehicles are more likely to cause accidents."
The coach involved in the M4 incident has been moved to a garage in Oxfordshire where it will be examined by accident investigators.
Police have confirmed no other vehicle was involved.
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