Highways England has warned drivers of long delays on the M1 near Northampton following a serious crash.
All three lanes southbound between junction 15 for Northampton and junction 14 for Milton Keynes have been closed today (Wednesday) following a crash involving a van and a lorry.
The accident happened at around 10.15am leaving one person trapped in a vehicle, according to traffic reports.
All lanes northbound between J14 and J15 were temporarily shut to allow for the air ambulance to land on the carriageway and re-opened again at 11am.
Southbound remains shut with emergency services deal with the incident.
Queuing traffic at the scene has been left trapped on the carriageway following the closure, while other drivers are being diverted ahead of the incident.
Highways has advised that trapped vehicles will be turned around shortly.
A spokesman said: "We have now begun turning the trapped traffic around. We will have you all moving real soon. Please remain stationary until advised by #TrafficOfficers"
The following diversion is in place: Follow Hollow Circle. Off at #J15, onto #A508 south, to #A5 south and then on to the #A509 to rejoin at J14.
Anyone travelling south is being advised to exit the M1 at J19 and to use the A14.
A spokeswoman for Northamptonshire Police said: "We confirmed that the M1 southbound is closed from junction 15 and we are about to close it from the slip road.
"We are dealing with a serious collision that happened just after 10am, which looks like a van and lorry."
A spokesman for Highways England confirmed that the collision involving a van and HGV occurred on the southbound carriageway, adding that emergency services were on the scene dealing with the incident.
Stagecoach Midlands tweeted: "Due to the closure of the M1 southbound between junctions 15 and 15a, we are experiencing severe delays to our X6 and X7 services.
"Should the resulting congestion continue, this may also cause delays to our number 7 service. Apologies for any inconvenience caused."