The closure was put in place on the northbound carriageway between junctions 32 (Broughton Interchange) and 33 (Hampson Green Interchange) at approximately 4.30pm.
Traffic officers, police and paramedics have been called to the scene.
No details have been released about the number of vehicles involved, but "considerable delays" are expected.
A spokesman for Highways England said: "This full closure will be in place for several hours."
The collision has caused several miles of congestion on the M6 around Preston and the M55 eastbound from Blackpool.
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Serious crash closes M6 northbound in Lancashire
Last updated: Friday, 13 August, 2021, 12:07
- The northbound was closed between junctions 32 (Broughton Interchange) and 33 (Hampson Green Interchange)
- Traffic officers, police and paramedics have been called to the scene
- Highways England said “considerable delays” are expected
- Carriageway not expected to reopen until at least 8.15pm
Updated traffic map of the area
60 minute delays
Highways England are now reporting 60 minute delays on the M6 northbound in Lancashire.
The carriageway is not expected to reopen until at least 8.15pm.
Closure affecting traffic on the M55 eastbound
Latest update from Highways England:
Latest pictures from the scene
Investigation works will be taking place
Due to the severity of the incident, collision investigation works will be taking place which are expected to take some time.
Latest congestion map of the area
Heavy congestion has been building in the area: