The M6 is closed in both directions between junctions 27 and 28 this evening after a serious crash just before 7pm.
The air ambulance landed around half an hour later. Just before 9pm, police said the motorway is unlikely to reopen before midnight.
A spokesman for Highways England said: "The M6 in Lancashire is closed northbound between J27 (Parbold, Standish, Chorley, A5209) and J28 (Leyland, B5256) due to a serious collision. Lancashire Police, Fire & Rescue and North West Ambulance paramedics are on scene. The southbound traffic has been stopped prior to the scene also to allow an air ambulance to attend the scene.
"A diversion is in place for northbound traffic.
"Exit at J27 and follow the route marked with a hollow yellow diamond symbol on road signs.
"This will take traffic via the A5209 eastbound. At the junction with the A49 turn left on to that road and head north.
"At the junction with the A581 turn right on to that road and head east. At the roundabout with B5252 take the first exit and head north.
"At the roundabout with Euxton Lane take the first exit and follow Euxton Lane west. At the junction with Central Avenue head north (on Central Avenue) past Buckshaw.
"At Buckshaw Green continue forward on to the B5248 west to the junction with the A49. Turn right on to that road and head north. At the junction with the B5256 turn left and head west to rejoin the M6 at J28.
"The road is expected to remain closed northbound for several hours. Southbound traffic should be released once the air ambulance has departed the scene.
"Please allow plenty of additional time for your journey if your intending on travelling in the area tonight. If possible please consider alternative routes."
Lancashire Police has advised people to avoid the area. A spokesman said: "We are currently at the scene of a serious collision close to junction 27 of the M6 near Charnock. The motorway has been closed in both directions. We would ask motorists to please avoid the area if possible. We will update as soon as we can."