The A14 between Huntingdon and the A1(M) could remain closed “for several hours” after a lorry overturned.
The accident happened on the northbound stretch between the Spittals interchange at junction 23 and the A1(M) just before 10am. The driver of the lorry, which was carrying clothing, was not injured.
Traffic has been reported as queuing as far back as junction 26 for St Ives.
A spokesman for the Highways Agency described “significant delays” and said drivers were being diverted along the A14 to junction 22, then onto the A1.
Motorists are advised to avoid the A14 as route is likely to remain closed for several hours, added the spokesman.
Cambridgeshire Police have warned the road could stay shut for six hours.
The overturned lorry follows two earlier crashes on the A14 this morning, one involving three vehicles on the eastbound carriageway between Huntingdon and Godmanchester at about 9.30am.
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