Traffic was moving slowly along the motorway in the Preston area following the smash on the southbound carriageway on Thursday evening.
The collision, between junctions 30 and 29, was causing queues back up to junction 32 at Broughton.
Highways England said motorists were facing delays of around half an hour.
Shortly after 6.15pm, a spokesman said: "On the M6 southbound between junctions J30 and J29, there are currently delays of 30 minutes caused by congestion due to an accident closing one lane between junctions J32 and J30. Normal traffic conditions expected from 7pm."