The air ambulance has landed on the main route between Whitby and Scarborough after a serious crash.
North Yorkshire Police closed a stretch of the A171 at Harwood Dale at around 1pm.
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It is likely to remain closed for some time.
The fire service, ambulance and the air ambulance are all at the scene.
North Yorkshire Police tweeted: "We are dealing with a collision on the A171 near to the junction to Harwood Dale between Scarborough and Whitby.
"The road is likely to remain closed for some time. Please avoid the area whilst emergency services respond.
"Diversion is via the #A170 and #A169."
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The police are unable to give further details on injuries at this time.
There has also been a crash on the A169 near Fylingdales. The road is still open but there are extra delays due to the A171 closure.