Part of the M6 southbound is closed around junction 10 for Walsall, West Midlands, after a crash involving at least two HGVs.
Traffic is queueing for more than six miles towards the junction 10a for the M54 near Featherstone.
Birmingham Airport, around 20 miles away, has warned travellers to allow extra time for their journeys.
The crash involves a number of vehicles, including HGVs, and emergency services believe there has been a fuel spillage.
It is understood to have happened at around 5.30am.
West Midlands Police and other emergency services remain at the scene.
It’s thought some 28,000 litres of low hazardous liquid has covered the motorway.
“The collision involved two lorries and there’s currently three lanes blocked off because of a considerable leak on the southbound carriageway.
“Environmental Health has been called to assist. Highways England are still on-scene.
“We have no idea at this stage of when the lanes will reopen,” a spokesman for the police force said.
There is believed to be one minor injury.
The stretch of the motorway is often busy as M54 traffic merges from the west.
Traffic from the M5 joins the northbound carriageway around seven miles away.
But northbound traffic on this occasion is unaffected, Highways England says.