An air ambulance has been called after the pile-up on the southbound carriageway near junction 12 for Toddington and Harlington, Bedfordshire. The road is closed southbound between junction 13 for Woburn and Brogborough and traffic is slow northbound approaching junction 12.
The crash, which happened at around 8.20am, is causing 90 minutes of delays southbound, reports Buckinghamshire Live.
A separate incident, involving an overturned lorry near junction 14, has added to the congestion.
A National England spokesman said: “The M1 southbound is currently closed between J13 Brogborough and J12 Toddington. This is due to a serious collision involving multiple vehicles.
“The northbound carriageway is temporarily blocked to facilitate air ambulance.
“All emergency services are in attendance with National Highways Traffic Officers deployed to assist.
“Please be aware there are severe delays up to 90 minutes approaching J13. There is approximately 14 miles of congestion on the southbound carriageway approaching J13. This incorporates congestion following an earlier incident between J15 and J14.
“There is 2 miles of congestion approaching J12 northbound with delays also building up to 90 minutes.
“Road users are advised to expect disruption and allow additional time for their journey.”
Inrix, the traffic data company, said: “Long delays and queueing traffic for eight miles due to earlier overturned lorry on M1 Southbound between Newport Pagnell Services and J14 A509 (Milton Keynes). Congestion to J15 (Northampton).”
Local roads through Woburn and Milton Bryan are busy as traffic leaves the motorway at junction 13.
Some northbound drivers are leaving at junction 11a to use the A5 through Houghton Regis, Bedfordshire, and nearby Hockliffe.