POLICE are appealing for witnesses to a collision on the M4 in the early hours of today.

At approximately 00.20am a four vehicle crash occurred on the eastbound carriageway, between junction 15 and Membury Services.

A blue Ford Transit van lost control and overturned onto the carriageway. As a result of this, a black Audi stopped in the vicinity.

The occupants of both vehicles were believed to be standing at the side of the carriageway when a car transporter collided with both vehicles and occupants.

The driver of the Audi, a 32-year-old woman from the Salisbury area, sustained life threatening injuries.

The passenger in the Ford Transit sustained serious injuries and the driver minor injuries.

The woman and the Transit passenger were airlifted to Frenchay Hospital and the driver of the Transit taken by land ambulance to the Great Western Hospital.

The driver of the car transporter was arrested at the scene for causing serious injuries by dangerous driving. He remains in police custody at Gablecross Police Station.

The driver of an articulated vehicle, which was damaged as a result of the collision, was uninjured.

The motorway was initially closed in both directions to allow officers from the Wiltshire Police Serious Investigation Team to examine the scene.

Lanes one and two of the westbound carriageway were subsequently opened to traffic but the eastbound lane remained closed throughout the night for the investigation to be carried out.

The motorway was eventually reopened at around midday after the vehicles had been recovered and the carriageway made safe.

The collision is being investigated by PC Alan Hunt of the Serious Collision Investigation Team.

Any witnesses are asked to contact PC Hunt on 101 or Crimestoppers on 0800 555 111 where information can be left anonymously.