A 13-year-old boy remains in a critical condition in Frenchay Hospital, near Bristol, and his mother is being treated at Salisbury District Hospital following a car crash on the A360 near Devizes on Sunday morning.

The mother and son, who are understood to live locally, were rescued from a black Citroen C3 which left the road while it was negotiating a bend between the turning for Great Cheverell and Black Dog crossroads.

The car ended up in a brook and firefighters from Devizes, Melksham and Trowbridge rescued them from the car as it was filling up with water.

Great Western Ambulance Service sent two paramedics in cars, two ambulance crews, the Great Western Air Ambulance from Filton, its Hazardous Area Response Team and a SWIFT medic.

The mother suffered facial injuries and was treated at the scene before being taken by road ambulance to Salisbury District Hospital. Police said today her condition is not life threatening.

Her son suffered serious, life threatening injuries. He was treated at the scene and stabilised before being flown by the air ambulance to Frenchay.

Police said today he is in a critical condition.

The accident happened just after 10am. The car was driving towards Devizes. Witnesses are asked to call Wiltshire Police’s serious collision investigation team on 101.

There have been other accidents at the same bend, including one in 2009 when a motorist ended up in the brook. She was rescued by a passing motorist and PC Tom Kinderman.

The speed limit on the A360 was changed recently from 60mph to 50mph as part of a wider Wiltshire-wide speed limit review.