An air ambulance has been called to a serious crash on the M4 thought to involve three cars.

The crash between junction 14 and junction 15 has completely closed the M4 in both directions.

The crash was first reported at 3:31 pm and has led to two miles of congestion according to National Highways.

The circumstances of the crash are currently unclear. The AA reports that ‘there have been three separate accidents between J14 and J15’.

However, National Highways has said that the closure is due to ‘a multi vehicle collision’.

Emergency services including Wiltshire Police are in attendance and National Highways Traffic Officers are also in attendance.

The M4 westbound is now closed between junction 14 and 15, and eastbound is also being held to allow an air ambulance to land at the scene.

The AA has also reported there as being surface water in the area, warning to approach with caution, though it is not known if this is involved in the accident.