North West Motorway Police confirmed a serious road traffic incident took place on the M6 southbound between junction 28 and j27.
Lancashire police, paramedics and an air ambulance have been called to the scene.
A Lancashire Police Force Incident Manager said a HGV had collided with a bridge at J27.
All traffic was held before 12:30pm while emergency services rushed the scene, AA route planner reports.
Highways England warns motorists to expect queuing traffic of up to four hours.
In a post on Twitter, North West Motorway Police said: “Patrols are now on scene at the Serious RTC on the M6 at J28 to J27 Southbound,
“We will need to close the NB for Air Ambulance to land.
“The traffic is stopped whilst emergency services deal with the incident Live lane.”
A Lancashire Police Force Incident Manager told Lancashire Live: “North West Motorway Police are leading this incident.
“We have closed the bridge over junction 27 as a precaution.
“It’s a HGV that’s collided with a bridge.
“We are supporting North West Motorway colleagues.”
More to follow