Swiss investigators are examining whether the design of a tunnel contributed to a school coach crash which killed 28 people.
A British boy, 11-year-old Sebastian Bowles, was among the 22 children who died following the accident inside the Tunnel de Geronde near the town of Sierre in Switzerland.
The coach is believed to have clipped a kerb inside the tunnel and veered into a lay-by which ended at a solid brick wall.
The Swiss Federal Office for Roads said it was examining whether the angle of the wall increased the severity of the crash. A facility to help disabled vehicles meant it was at a right angle to the tunnel road.
Spokesman Michael Mueller told The Associated Press: "In principle there is the possibility of slanting the angle of the bay, or protecting it with concrete or other elements."
He added: "Such a severe and tragic accident must always be taken as an opportunity to analyse the factors that could have influenced the causes and effects of the disaster."
Meanwhile Olivier Elsig, prosecutor for Valais, the region where the town is located, said investigators are studying three possible causes: human error, a health problem with the driver or a technical problem with the coach.
With some of the 24 recovering crash victims beginning to talk about their ordeal, Belgian and Swiss newspapers were speculating that the coach driver might have been involved in efforts to change a disc on the coach's entertainment system shortly before the crash.
The 52 people onboard were returning from a ski holiday in the Swiss Alps.
Sebastian's British father Edward and Belgian mother Ann returned to Belgium from Switzerland last night after identifying their son's body.
The family moved to Belgium only two years ago to be close to Mrs Bowles's relatives.
Mr and Mrs Bowles lived in Crouch End, north London before moving to Belgium where Sebastian joined St Lambertus School in Heverlee.
Like other pupils on the trip he had used a school blog to express delight at his emerging skiing skills.
Before he moved to Belgium, Sebastian was a pupil at Our Lady of Muswell Catholic Primary School in north London. Sebastian, referred to by staff as "the little cherub", was a pupil at the school between 2003 and 2009.
In a statement read out on the school steps, headteacher Teresa McBride said: "Our school community is still reeling from the shock of this terrible accident. Our thoughts and prayers are with Sebastian's family at this tragic time.
"He was a wonderfully vibrant boy who is so fondly remembered by pupils, staff and parents at Our Lady of Muswell. He was known by staff as the little cherub. He will be greatly missed.
"Today the school held a one-minute silence to remember Sebastian."
Belgium has also marked the deaths with a minute's silence, observed by schoolchildren, politicians, factory workers, shoppers and motorists across the country.
Travellers at bus, underground and railway stations were asked to pause until church bells rang out to sound the end of the moment of remembrance, the centrepiece of what was declared a national day of mourning within hours of Monday's accident.
Parents stood in silence at the schools in Lommel and Heverlee, which lost a total of 22 pupils. The other victims were teachers from the schools and the coach's two drivers.
Three military planes repatriated the bodies of the victims, now all identified. Hearses then carried the bodies back to their respective home regions around Heverlee and Lommel near the Dutch border.
Swiss authorities said 12 more injured children were repatriated today.
A hospital spokeswoman said the children, most of whom were Belgian, were taken home by special medical transport flights. Eight injured children travelled home with their relatives yesterday.
The spokeswoman told reporters that three children are still being treated at a hospital in Lausanne and one is at a clinic in the capital Bern.
Meanwhile in Brussels, government officials and politicians gathered in rows outside buildings. At European Commission headquarters, flags were flying at half-mast.
Some commercial television stations halted transmissions for much longer than one minute, cancelling many programmes altogether.