The driver of a van that collided with a horsebox on the A11 near Attleborough died at the scene of the crash.
Police said he was in his 30s and was the only occupant of the vehicle. His family has been informed.
The collision happened at 3.37pm on the northbound carriageway of the A11 just before the junction for Spooner Row.
Three people were in the horsebox vehicle, and one, a woman, was taken to hospital for treatment to minor injuries.
Two horses who were in the horsebox were unhurt, and another horsebox was sent to the scene to remove them.
Police said a considerable amount of debris on the road needed removing, and thanked those caught up in the traffic delays for their patience and understanding.
They said they would, in particular, like to speak to the driver of red Toyota MR2 vehicle that may be able to help with the investigation.
Anyone who witnessed the collision should contact the Serious Collision Investigation Team at Wymondham police on 101.
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