Belgium held a national day of mourning on Friday, including a minute of silence, for the 22 children and six adults who were killed in a coach crash in Switzerland on Tuesday.

As Belgians observed a minute of silence to honor the dead at 11:00am (1100 CET) today, flags flew at half mast, white balloons were released and church bells could be heard ringing. Buses, trains and metro services ground to a halt following a half-hour private ceremony. Meanwhile, the victims' remains were transported via Belgian military planes from Sion, Switzerland.

"The whole country weeps for its children," Prime Minister Elio Di Rupo said in parliament on Thursday.

The return of the victims' bodies comes a day after their parents undertook the grueling ordeal of identifying them. Some of the victims' injuries were so horrific that it was impossible to identify them, so DNA testing had to be carried out instead. The families also visited the site of Tuesday's accident in a tunnel in the Swiss Alps.

Watch video 01:18 After the bus tragedy: A national day of mourning in Belgium

The victims included 22 Belgians and six Dutch citizens. An additional 24 were wounded in the crash.

Six of the surviving children flew into Melsbroek military airport on Thursday night before returning home, with police escorts. A Swiss hospital spokesperson said another two were also due to be discharged. The other injured parties remain in hospital, with three in a critical condition.

The bus was transporting school children, mostly 12 year-olds from the Belgian towns of Heverlee and Lommel, following a week-long ski trip, when the driver crashed into the wall of a tunnel on Tuesday night.

Questions unanswered

The reason for the crash is still unknown. Speculation is rife as Swiss authorities continue to carry out autopsies on the bus drivers' bodies for clues of what went wrong.

Yves Mannaerts, director of the Belgian coach operators' association, has disputed suggestions that the drivers were tired or driving under the influence of alcohol.

"There is no question of it. On that issue, the contact with the Swiss authorities has been clear - there was no problem," Mannaerts said.

Some Belgian and Swiss media reported that, according to some of the surviving children, the driver lost concentration just before the crash whilst trying to insert a DVD. Olivier Elsig, the Valais prosecutor who is investigating the crash, has raised skepticism about this.

"A certain number of children were questioned and we took a series of statements. But they do not shed light on the cause. Personally I deeply doubt that if this did happen, that it could have played any role whatsoever," he said on Swiss television.

Christian Varone, chief of police of the Swiss canton of Valais, where the accident happened, said the police will take the witness statements of surviving children into account as they continue their investigations into what caused the horrific tragedy.

sej/sjt (AFP, Reuters)