Motorists were severely delayed after a serious crash on the M1 near Northampton this afternoon.
All lanes south and northbound between junctions 15a for Northampton to 16 for Daventry were originally shut to allow an air ambulance to land following the incident at around 2pm.
But the northbound side and two lanes southbound reopened at around 3pm after the air ambulance left the scene.
At 3.30pm all lanes reopened, Highways East Midlands has reported.
A spokeswoman for Northamptonshire Police has so far confirmed that the incident is a "serious" road traffic collision.
A spokeswoman for East Midlands Ambulance Service added: “We received a call at 13.37 hours today to the M1 between junctions 16 and 15a in Northampton.
"The caller reported a road traffic collision. We sent two ambulances, two fast response cars, and the air ambulance. We transported one patient to Northampton General Hospital by road ambulance.”