Motorists are being warned to allow extra time this afternoon after crash on the M1 this morning.
Highways England said emergency carriageway resurfacing were taking place this afternoon on the M1 northbound near Watford Gap.
The work comes after a collision between two HGVs overnight led to an oil spillage and damage to the road.
Since then two lanes of the motorway have been closed between junctions 16 (Flore) and 17 (for the M45 to Coventry), but this afternoon the entire northbound side has been closed to allow the work to take place.
Highways England initially said it expected the resurfacing to be complete by 3pm and to reopen the northbound motorway shortly after. But an update issued at 4pm stated the work was still under way.
The closure has led to delays on the A45 between the M1 and the A5 at Weedon, and knock on traffic on the A5 north back to the M1 at Crick and A45 through Daventry to Coventry. Drivers are being advised to find alternative routes and plan their journey.