The A141 is closed in both directions at Wyton following a crash.
Police shut off the road at the roundabout with the B1090 Sawtry Way this afternoon.
The accident happened between Sawtry Way and Oldhurst.
Drivers were warned to avoid the area and use alternative routes as delays built up, including in Houghton between the Mere Way junction and the A1123 Houghton Hill Road.
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