A child has suffered fatal injuries, and her 11-month-old brother remains in a critical condition after the vehicle they were travelling in crashed on the New England Highway near Willow Tree tonight.

About 7pm (Monday 17 August 2015), a woman was driving her sedan northbound on the highway, about 4km north of Willow Tree, when the vehicle rolled, landing down an embankment off the side of the road.

A passer-by stopped and assisted, locating a two-year-old child deceased, and an 11-month-old boy suffering critical injuries.

Police from Oxley and Hunter Valley Local Area Command’s attended the scene and co-ordinated a response with the assistance of NSW Ambulance, Rural Fire Service, VRA, and Westpac Rescue Helicopter.

The infant was flown to John Hunter Hospital where he remains in a critical condition.

The woman, who is the mother of the children, was taken to Tamworth Base Hospital where she remains in a stable condition.

Crash Investigators from Tamworth are on scene and will conduct a full investigation, and a brief will be prepared for the Coroner

Anyone who may have witnessed the crash is asked to contact the Crash Investigation Unit at Tamworth on (02) 6768 2890, or Crime Stoppers on 1800 333 000.