A truck has exploded on the M1 Pacific Motorway after crashing into three other trucks.

The vehicle became engulfed in flames on the NSW Central Coast near Halloran just after 2am Wednesday (30th October).

The truck was reportedly going through a roadworks zone when it plunged into three parked trucks, and immediately burst into flames, spreading to the other vehicles.

No injuries have been reported.

Traffic delays are expected throughout the morning, with all northbound lanes closed.