The northbound M6 is likely to be closed all day between J39 near Shap and J40 at Penrith.
The closure also involves one southbound lane and followed an HGV overturning near Eamont Bridge around 8.30am.
According to National Highways, there are delays of 30 minutes and congestion of three miles.
A statement says National Highways traffic officers, police and recovery personnel are at the scene, involved in a “complex and protracted recovery and clear-up operation”, with a “significant diesel and oil spillage across all lanes including the hard shoulder”.
The suggested diversion route is to exit the M6 at J39, turn left on to the B6261 westbound, then right at its junction with the A6 and head northbound through Shap, Hackthorpe, Clifton and Eamont Bridge. At the Kemplay Bank roundabout, drivers should take the first exit onto the A66 westbound and then rejoin the M6 at J40.
