The accident, involving two HGVs, a van and a car, happened around 5am today (Tuesday) between junction 30 near Rothwell and junction 31 near Castleford.
The motorway is closed eastbound between junctions 30 and 31 and westbound between junctions 30 and 32 at Pontefract.
There are no reports of serious injuries.
Drivers have been warned they face heavy congestion and queuing traffic in the area.
It is not known when the road will reopen.