*All lanes reopened at around 1.10am on Thursday (December 9).
All traffic was stopped on the southbound carriageway between junctions 8 (Chorley North Link Interchange) and 6 (Horwich Interchange) at around 2.40pm on Wednesday, December 8.
This was due to a diesel spillage and extensive barrier damage following a multi-vehicle collision, National Highways said.
Approximately four miles of stationary traffic was reported in the area, with motorists urged to consider alternative routes.
One out of three lanes reopened at around 3pm but heavy congestion and "60 minute delays" remained.
A spokesman for Lancashire Police said: "We have closed two lanes on the M61 southbound between J8 (Chorley) and J6 (Middlebrook) due to a collision.
"Traffic is heavy in the area while we deal with the incident.
"Please bear this in mind if your journey takes you this way and consider alternative routes."
At 6.08pm, National Highways confirmed two lanes were running past the scene on the southbound carriageway, but one lane had been closed on the northbound side.
"1 lane (of 3) remains closed on the M61 southbound between J8 (Chorley) and J6 (Horwich) due to an earlier collision which has resulted in central reservation barrier damage," a spokesman added.
"Lane 3 will also be closed on the northbound.
"There's now just over a mile of congestion on approach."
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