The large set of ladders has reportedly fallen onto the M6 northbound, between junctions 27 (Charnock Richard Services) and 28 (Leyland), at around 2pm (June 18).
Motorway police have informed Highways of the obstruction, which has been straddling all three lanes of the carriageway.
Police said vehicles are being forced to swerve suddenly to avoid the dangerous obstruction.
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The bulk of the ladders lies in lane 2, but both its ends are straddling lanes 1 and 3.
Highways officers are en route to recover the ladders and secure the carriageway.
North West Motorway Police said: "We have taken a report of a set of ladders in the live lanes across all 3 lanes.
"Vehicles seen swerving on the M6 between J27 to J28 northbound. Highways have been deployed."