The M4 has been closed in both directions due to a person in distress on an overbridge.
Police were called to a footbridge over the motorway between junctions 16 and 15 at around 2pm this afternoon (18 March).
Police vehicles are lining Pipers Way as officers response to the incident.
A Hazardous Area Response Team (HART) from a South Western Ambulance Service hub in Bristol is also in attendance.
Two specialist police negotiators arrived shortly before 2.45pm.
Jacobs Ladder — part of the Croft Trail — is also closed by police.
A spokesperson for Wiltshire Police said: “Drivers, please be aware that the M4 is currently closed between junctions 15 and 16 while officers deal with an incident on an overbridge in Swindon.
”Please avoid the area if possible.”