The A19 is closed both directions at Exelby Services in North Yorkshire due to a spillage of hazardous material from a lorry.
North Yorkshire Police said the the road is closed Southbound from the Crathorne Interchange and Northbound from the Cleveland Tontine.
A spokesperson for the North Yorkshire Fire and Rescue Service said: "We are in attendance on the A19 at the Exelby Services, where a lorry carrying hazardous material had a leak.
"One of the containers has leaked and that has gone into the septic tanks at the services it has pulled up at.
"We dispatched two appliances. Cleveland Fire and Rescue Service, also sent two appliances. The incident was reported at 6pm."
The AA said a detour in operation via the A67, the B1264, the A167.
Motorists have been urged to avoid the area wherever possible.
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