Traffic is queuing on the A14 in west Suffolk after a crash involving two cars.
National Highways said on Twitter lane one of the westbound carriageway, between junctions 37 and 38 near Newmarket, had been closed.
Police from Cambridgeshire Constabulary have been called to the scene.
National Highways said the incident was causing delays of up to 40 minutes in the area.
The AA traffic map says drivers are queuing back as far as Kentford – a distance of about seven miles.
For up-to-date information about the county's roads, visit our LIVE Suffolk traffic map.
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