BOLTON, Ont. -- No one was hurt when a school bus collided with two other vehicles and rolled into a river in southern Ontario this morning.

It happened at the corner of Humber Lea Road and King Street East in Bolton, Ont.

Provincial police say the bus was climbing a hill with 17 high school students on board when it stopped, rolled backwards and collided with two passenger vehicles -- a Jeep and a Ford Focus.

Police say several other vehicles managed to steer clear of the bus, and no one involved was injured.

The bus eventually rolled into the Humber River and its back end became partially submerged.

Provincial police say the road was closed for about two hours and the incident is under investigation.