UPDATE: One man is trapped inside a truck and suffering from severe leg injuries, after being involved in a serious two-truck crash in the Wheatbelt.

The RAC rescue helicopter has been sent to the scene of the crash near the intersection of Albany Highway and Marradong Road in Williams.

At least one man has sustained severe injuries but other people are also through to be hurt in the crash. A doctor is at the scene helping emergency crews.

The cause of the crash, which happened about 12.45pm, is unknown.

Motorists are asked to avoid the area, with roads being closed.

Meanwhile, a man has been involved in a car rollover near Busselton, after the vehicle he was in hit a tree.

The crash happened on Vasse Highway in Yoongarillup shortly before 1pm.

His injuries are not thought to be serious.