Belgian families in mourning prepare to visit the Swiss mortuary where their loved ones are being kept after Tuesday night's coach tragedy.

Twenty-eight people died when a coach carrying a group coming back from a school trip slammed into the side of a tunnel.

Twenty-two of those who died were children, mostly from this school in Belgium where pupils and teachers were grieving.

The school pastor said classes have resumed with special programmes focused on explaining to the children what happened to their classmates.

(SOUNDBITE) (Dutch) SCHOOL PASTOR AND DEAN OF LEUVEN, DIRK DE GENDT:

"It's very important for children that their daily routine continues, they need a stable frame as their reference, to survive, that way it is easier to give their emotions a place."

A mother of one of the pupils at the school sympathised with the difficult task that teachers face.

(SOUNDBITE) (English) MOTHER IZABELA KUZMA:

"The teacher will try to tell or maybe better explain to kids what's happened, so I think it is of course very tough... very hard."

Swiss officials say there were three possible causes of the crash - a technical problem, driver illness or human error.

Simon Hanna, Reuters.