The driver of the Belgian coach which crashed in Switzerland killing 28 people had no trace of alcohol in his blood, an autopsy has revealed.
Swiss prosecutors also said that there was nothing to support the theory that the accident was caused by illness.
The autopsy results came as Belgium held a national day of mourning to remember the victims of the crash.
The accident happened on Tuesday when the coach hit the wall of a tunnel on the way back from a school skiing trip.
Most of the victims were Belgian children - six had Dutch nationality; one was British. All six adults on the coach died.
Eight of the injured children were flown home on Thursday and reports say 12 more children were flown back to Belgium on Friday.
The four most seriously injured children are being treated at hospitals in Lausanne and Bern.
The bodies of those killed have been brought back to Belgium. A convoy of hearses left Melsbroek military airport, carrying the white coffins.
It is unclear what exactly caused the crash but Swiss prosecutors were swift to discount alcohol.
"An analysis did not show alcohol in the driver," prosecutor Olivier Elsig said, while giving the results of an autopsy.
The authorities have also refused to comment on suggestions in Swiss and Belgian media that the coach driver may have been changing a DVD at the time of the crash.
Swiss police spokesman Renato Kalbermatten said CCTV from the tunnel did not confirm the disc theory, which he described as "pure speculation at this stage".
Police have also said that they did not believe the coach was speeding at the time of the crash.
Crash site flowers
On Friday Belgium came to a standstill for a minute's silence at 11:00 (10:00 GMT) and flags were flown at half mast. After the minute's silence, church bells rang out.
Family members of the dead children who had travelled to Switzerland visited the crash site on Thursday, some laying flowers in the tunnel.
The group had spent a week skiing in Val d'Anniviers in the Swiss Alps and were travelling home on one of three buses hired by a Christian group. The other two coaches reached Belgium safely.
Those on board the bus that crashed were from the Stekske primary school in Lommel, near the Dutch border, and from St Lambertus in Heverlee, near Leuven (Louvain).
Lommel's mayor announced that the town would hold a memorial ceremony next Wednesday.
Peter Vanvelthoven said the Belgian royal family and the Queen of the Netherlands would attend.
It would be an interfaith ceremony, at the parents' request, he added, "in which every one of those families can say goodbye in a dignified and respectful manner".