The A1(M) northbound carriageway between Welwyn and Stevenage has now reopened after a closure was put in place following a collision which resulted in the death of a horse.
The southbound road remains closed at Junction 7 for Stevenage after a Land Rover and horsebox - containing two horses - overturned.
A second horse is thought to be seriously injured.
Police were called to the scene at 2.25pm and an ambulance also attended as a precaution for two female occupants of the Land Rover.
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