Long queues have formed on the M1 near Northampton after several vehicles were involved in a crash.
Emergency services have been forced to close a stretch between junction 16 and junction 18.
Reports suggets a multi-vehicle accident on the southbound carriageway in the construction area near Watford Gap Services.
As a result there is stationary traffic and a detour is in operation.
Drivers are being advised to exit at junction 18 and follow the hollow square symbol.
Official advice is to take the A5 south, then the A43 east to re-join the M1 at J15A.