All lanes of the New England Highway are now open at the site of a car crash at Whittingham.
The highway was closed in both directions due to the crash near Range Road.
Diversions have now been lifted but traffic is still heavy in the area.
A woman and child were taken to hospital in a critical condition after the crash.
Emergency crews were called to the scene on the New England Highway at Whittingham, about 500 metres north of Range Road, at 11.15am after reports of a head-on crash between a car and a four-wheel-drive.
NSW Ambulance crews treated five patients - one was air-lifted to hospital while the others were transported by road.
A Westpac Rescue Helicopter spokesperson said a six-year-old boy was taken to hospital by chopper.
Police said the female driver of the car and a child were in a critical condition as of 12.30pm.
They said two other children and a man - who was the driver and sole occupant of the four-wheel-drive - were being treated for non-life-threatening injuries.
THE New England Highway has been closed between near Singleton after a serious crash on Friday morning.
The two-car collision occurred just before 11.15am near Haggartys Lane in Whittingham.
Emergency services were called to the scene after reports a car and a 4WD had crashed head on. They remain at the scene and are working to treat one patient still trapped in a car.
The female driver of the car and a child passenger are in a critical condition.
Two other children are also being treated for non-life-threatening injuries.
The male driver and sole occupant of the 4WD has been taken to John Hunter Hospital with non-life-threatening injuries.
The Westpac Rescue Helicopter was also tasked to the scene.
Police have closed the road in both directions, and motorists are being diverted via Range Road, but heavy vehicles are being ordered to park at the scene.
The RMS said a diversion via the Golden Hwy (Mitchell Line of Rd) and Putty Rd will allow motorists to travel between Whittingham and Singleton.
Authorities urge drivers to allow an extra 25 minutes travel time.
Light vehicles already in the area are being diverted into Range Rd.
Officers from Hunter Valley Police District have established a crime scene as they investigate the circumstances surrounding the crash.
Anyone with information about this incident is urged to contact Crime Stoppers: 1800 333 000 or https://nsw.crimestoppers.com.au.
More to come.
WHITTINGHAM: New England Hwy is closed both ways near Range Rd after a two-car crash. Avoid the area. If you are already in the area your're being diverted into Range Rd. Consider using Golden Hwy and Putty Rd instead. Traffic's heavy so allow extra time. pic.twitter.com/MXsdG3G3Kg— Live Traffic NSW (@LiveTrafficNSW) July 12, 2019