A lorry has crashed through barriers of a motorway and been left overhanging the side of a bridge.
The M25 has been closed anti-clockwise at junction 2 south of Dartford, Kent, and the A2 is shut in both directions as a result.
Highways England said a "complex recovery and repair operation" was under way and the roads would be closed for some time.
Kent Police said the driver was not seriously injured.
The crash in which part of the lorry's trailer went through the safety barrier was reported to Kent Police at about 13:20 BST.
There are delays to traffic on the M25 from junction 4 on the anti-clockwise carriageway, and over the Queen Elizabeth II Bridge on the clockwise carriageway.
"Significant damage" has been caused and congestion stretched 6 miles (10km) approaching the Dartford Crossing, a Highways England spokesman said.
Drivers have been warned to allow extra time for journeys if travelling in the area, or to consider alternative routes.