Driver flung out of truck after fiery explosion on M1

Five men have been taken to hospital after a B-double crashed into three cars and caught fire at a roadworks site on the M1 on the NSW Central Coast.

Emergency services were called to the road at Halloran at 2.10am.

The B-double hit a stationary roadworks truck and forced that vehicle into another two other RMS trucks, which were stopped on the roadside.

The force of the crash flung the driver out of his cab, and he suffered a shoulder injury.

One of the trucks also caught fire.

The driver will undergo mandatory testing, while four roadworkers were treated for shock. Three of the men remain in hospital.

Police said one witness reported that the truck appeared to be swerving at the time of the accident.

Chief Inspector Cole Lott from Tuggara Lakes Police District said the men were "very lucky" not to be more seriously injured.

"It's alleged that the driver was ejected from the cabin of his vehicle, however it's believed he only sustained minor injury to his shoulder," he said.

There were traffic queues of up to 9km earlier. All roads have now reopened, but delays remain.

Police are calling for anyone with dashcam vision of the incident to contact Wyong Police or Crime Stoppers on 1800 333 000.