UPDATE: National Highways has confirmed the motorway has since reopened.
The M4 is closed following a ‘police incident’ in Swindon this morning (Tuesday).
Emergency services are attending an unknown situation westbound between junctions 15 and 16. 
The National Police Air Service helicopter from Bristol arrived over the incident at 7.45am.
The closure is causing major delays on the eastbound carriageway, the A419 southbound and the A346 Marlborough Road.
A National Highways spokesperson said: “Due to a police-led incident, the M4 westbound between J15 and J16 near Swindon is now closed.
“Wiltshire Police are on scene. There are delays of at least 15 minutes in the area.”
