Four people were injured in a multi vehicle collision on the M1 southbound on Monday, October 27.
Motorists faced severe delays following the seven vehicle collision, between junctions 9 and 10, at 6.30am, all four lanes were closed.
Four people were taken to Luton and Dunstable hospital but the injuries are not believed to be serious.
An East of England Ambulance Service spokesperson said: “We sent three ambulances and one ambulance officer and treated four patients at the scene.
“One patient was boarded, and three further patients were assessed before being taken to Luton and Dunstable Hospital for further treatment.”
Six vehicles had to be recovered from the scene.
There were delays on the motorway back to junction 12 and delays of up to two hours in the surrounding area.
A spokesperson for Hertfordshire police said: “Officers are still investigating the incident.”