Emergency services have been called to a serious accident at Denman in the Upper Hunter.
It's understood a car and a truck collided head-on just after 4.00am on Tuesday on Denman Road about 12 kilometres south of Muswellbrook.
The condition of the drivers is not known at this stage.
Denman Road is closed in both directions between the Golden Highway and Edderton Road.
Light vehicles are being diverted via the Golden Highway and Edderton Road.
Heavy vehicles are being parked by the side of the road, otherwise truck divers are being urged to use the New England Highway and they're being advised to allow about 75 minutes in extra travel time.
Denman Road is likely to remain closed for some time.
