Police were called at 10.43am to reports of a collision involving a number of vehicles on the M62 eastbound, junction 22-23.
At least one person has been seriously injured.
One man has been arrested.
The eastbound carriageway has been closed and is likely to remain closed for some time while emergency services work at the scene.
Motorists are advised to avoid the area. All traffic has been held on the motorway in both directions for several hours, and drivers are slowly being released in the wrong direction while the road remains closed.
The M62 motorway diversion route currently in place
The M62 is closed in West Yorkshire, on the eastbound carriageway between Junction 22 (Saddleworth) and Junction 23 (Huddersfield A640) because of a crash.
Traffic is also being stopped on the westbound carriageway.
Police are on the scene with an air ambulance.
This is the current diversion:
Driving east, exit the M62 using J22 off slip and proceed to the end of the slip road.
-Turn left on the A672 and proceed until the A58 junction
Join the A58 (Halifax Road) and proceed along the road for 5 miles to the A6142
Go forward onto the A58 and proceed for 500m to the junction with the A646
Then turn right onto the A646 and proceed until the A629
Turn right onto the A629 and proceed for 4 miles until Ainley Top roundabout. Take the third exit onto the A629 and proceed for 500m to the junction with the M62 (J24)
At the roundabout, go 2nd exit to rejoin M62 East