At least 28 people - including 22 children - have been killed in a bus crash in Switzerland, police say.

瑞士一辆公交车发生车祸，至少28人死亡，这其中包含22名儿童。

Some of the injured were airlifted to nearby hospitals
Another 24 children were injured in the accident in the canton（行政区，州） of Valais, near the border with Italy.

The bus - which was carrying children from Belgium - crashed into the wall of a tunnel. Both drivers were killed.

The children from the Belgian villages of Lommel and Heverlee were returning home after a skiing holiday. There were 52 people on the bus.

The bus hit the wall of the tunnel near the town of Sierre on Tuesday night.
 
Two classes of schoolchildren from the Flemish-speaking part of Belgium were travelling home after spending a skiing week in Val d'Anniviers, in the Swiss Alps.

In Brussels, the Belgian foreign ministry¹ said most of the children were aged² around 12, and the bus was one of three hired by a Christian³ group, the AFP news agency reports.

Some of the injured were later flown by helicopters to hospitals in Lausanne, Berne and other Swiss cities.

Swiss journalist Ruth Seeholzer told the BBC that some 300 rescuers were working at the scene of the crash.

She said that the two-lane tunnel was not busy with traffic when the accident happened and driving conditions were normal.

Police described the crash as "unprecedented⁴".

An investigation⁵ is now under way.

A helpline for families has been set up, and many parents are expected to arrive in Switzerland shortly.