Belgium is mourning the death of 28 people, most of them children, who were killed in a bus crash following a ski vacation in Switzerland.

Distraught parents flew to Switzerland Wednesday to identify the dead and attend to the surviving children. Doctor Cawen Mechiel, who is treating some of the injured children at a hospital in Sion, says most of them have broken bones.

“Well the children who are here in the hospital in Sion — they are, of course considering the very heavy accident, they are in rather good shape. Most of them have fractures but none of them is in life danger. We have about 12 people who are already in the pediatric ward and one who is still in intensive care and another who is now actually being operated. But here in this hospital there are no problems concerning life-threatening events.''

The bus carrying 52 people back to Belgium after the skiing vacation struck the wall of a tunnel in the Valais region Tuesday evening. The accident mangled the front of the bus and left some of the passengers trapped in it. Police, firefighters and medical staff worked through the night to pull out survivors and bodies, while ambulances and helicopters took the injured to hospitals in the region.

Belgian Prime Minister Elio Di Rupo called it a tragic day for all of Belgium. He traveled to Switzerland Wednesday. Belgium's King Albert said his thoughts are with the victims and their families.

U.S. President Barack Obama also expressed his condolences and offered U.S. help if needed.

Belgian and Swiss authorities are still trying to determine why the bus slammed into the tunnel wall, but they say the vehicle traveled at a normal speed.

Among those killed were 22 children from two Catholic elementary schools in Belgium, most of them Belgian citizens and some foreign.