Drivers in Merseyside are being advised the M57 is closed in both directions between junction 4 near Knowsley and junction 6 at Kirkby.
The closure follows a serious collision between two cars at around 11am.
The motorway is likely to remain closed for several hours to allow a police incident investigation and drivers are being urged to review journey plans should they wish to avoid congestion.
There is already heavy southbound congestion back to Switch Island with the M58, A5036 and local roads.
A diversion is in place east of the motorway using the A506 Valley Road, A5208 County Road and A5207 Moorgate Road North.
Northbound drivers are being asked to follow the ‘yellow diamond’ symbol from junction 4; southbound drivers leaving at junction 6 should follow the ‘black circle’ symbol.
Highways England traffic officers are at the scene helping to manage traffic and free drivers stuck on the motorway behind the incident.
Colleagues at the North West Regional Operations Centre at Newton-le-Willows have set electronic signs across the regional motorway network to advise other drivers of the closure. Driver should consider delaying journeys or using alternative routes.
Live traffic information is available at www.trafficengland.com or from Highways England’s 24-7 customer contact centre at 0300 123 5000.