It is understood a van with a trailer may have jack-knifed near the Moira slip road city bound.
It appears the vehicles went over the barrier and into a hedge.
The PSNI and NI Ambulance were tasked to the scene. The area is now cleared.
“There were no reports of any injuries.”
One man said: “Just witnessed a bad accident on the M1 just before the Moira turn off.
“Van and trailer jackknifed and ended up going over the barrier into a hedge.
“Anyone heading that direction expect delays, it’s literally just happened and police and ambulances bombing down the motorway.”