Mounties say the driver of crane that went off a bridge and into a river in northwestern Alberta is missing.

RCMP say it happened near Grande Prairie on Tuesday, when the commercial vehicle hit a guardrail of the Wapiti River Bridge and went into the water.

Police, fire, and search and rescue volunteers responded to the scene.

Cpl. Mathew Howell says the vehicle remains submerged and the cause of the collision is under investigation.

Howell says divers haven’t been able to go into the river, because the current is too strong.

He says police plan to use sonar technology next week in their search.