The M55 westbound was closed between junctions 1 (Broughton Roundabout) and 3 (Wesham Interchange) at approximately 1.50pm due to a "police incident".
National Highways warned motorists that congestion was building on the approach.
At 2.20pm, it was confirmed the carriageway had fully reopened and traffic was easing.
"The police incident has concluded and traffic has now been released on the M55 westbound," a spokesman for National Highways said.
"There are no significant delays in the area."
Lancashire Police said they were unable to find anything on their logs about the incident.
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