'Distraction and fatigue' investigated after truck plummets from bridge

Distraction and fatigue are being investigated as the possible cause of crash that resulted in a truck plummeting from a bridge south-east of Melbourne.

Authorities were called to a bridge on Bass Highway in Bass after the crash just after 10.10am.

The 21-year-old driver of the truck is said to have veered left on the road before the truck mounted the guardrail and fell into the water.

The Springvale man was trapped for some time before being freed from the truck.

The driver has been airlifted to the Alfred Hospital with life threatening injuries.

He is being treated for serious head, chest and pelvis injuries. 

Police set up diversions on the road while they work to lift the truck out of the river. 

The Hazmat unit was also called to the scene.  

"We don't like seeing these crashes happening, we want people to get from A to B safety," Mr Pearce said.