A TANKER has exploded on the M1 south of Newcastle, closing the motorway in both directions.

The tanker exploded on the M1 at Cooranbong, 1km past the Freemans Drive interchange, just before 1pm.

One truck caught fire and a number of other vehicles have been involved, a police spokesman said.

Due to the strength of the fire, police and emergency services had to wait to get close enough to the crash to see what caused it.

The explosion has started a grassfire in the roadside bushland.

Fire crews have covered the tanker with foam as flames continue to leap from its front tank.

The front cab of the vehicle appears to have been destroyed.