At about 11.30pm, emergency services were called to the M1 at Morriset in the Lake Macquarie region.

They found a semi-trailer had crashed into a guard rail under the Mandalong Road overpass and caught fire.

Firefighters extinguished the blaze and an investigation into the crash is underway.

NSW Fire and Rescue said the truck had been “destroyed” in the fire.

The southbound lanes of the M1 are closed and diversions are in place.

Drivers are urged to avoid the area and delay non-essential travel.