A man was seriously injured when the truck he was driving collided with a freight train at Lake Poerua, between Rotomanu and Inchbonnie, about 50km south east of Greymouth, about 1.45pm on Tuesday.

The man had to be cut from the vehicle and was flown to Grey Base Hospital by rescue helicopter.

A Hokitika police spokesman at the crash scene said the man was the only person in the vehicle, which was an OnTrack truck.

The train, which was towing 14 wagons, was heading towards Greymouth and the incident occurred at a rail crossing controlled by a stop sign.