The southbound carriageway is shut in West Yorkshire between junction 41 for Outwood and East Ardsley and junction 40 for Wakefield and Ossett. Emergency services have dashed to the scene of the accident near the latter.
Traffic is being taken off the M1 at junction 41 and is sent through Wakefield itself, which is congested as a result this morning.
Tailbacks on the M1 are back past the M62 link and approaching junction 43 for Leeds.
Some drivers have been stuck in the jams for an hour, Yorkshire Live reports.
The northbound carriageway is busy as drivers slow to look at the collision. Drivers face delays from junction 39 for Durkar and Great Cliff.
Northbound motorists should, though, remain on the M1, authorities say.
And the M62 is congested as well, due to the pile-up.
Traffic monitoring system Inrix reports: “There is very slow traffic on the M62 westbound at J29 M1 J42 (Lofthouse) which is not helped by the problems on the M1.”
Highways England posted on social media: “M1 south between J41 and J40 Carrgate, Wakefield and Lofthouse.
“We are attending an accident which is severely impacting all lanes. Please plan an alternative route. Updates to follow.”
It later added: “FULL CLOSURE #M1 south between J41 andJ40 #Carrgate #Wakefield #Lofthouse Please take alternatives routes. Congestion is heavy in the area DIVERSION ROUTE Hollow square.”
West Yorkshire Police have been approached for more information.