Motorway traffic heading towards Northampton is queuing for more than four miles after a smash blocked all four lanes on the M1 southbound near Daventry on Wednesday morning (July 14).
Highways England reported emergency services re-opened two lanes to release trapped traffic between junction 19 and junction 18 at around 6.30am.
But they say severe congestion on the motorway and surrounding roads is likely to continue throughout the morning rush hour.
Firefighters from Northamptonshire and Leicestershire are at the scene along with East Midlands Ambulance Service paramedics.