A crash closed the A1065 near Fakenham.
The road was closed by police at 8.10am.
The incident happened in the Toftrees area and traffic is building in both directions, with tailbacks heading towards the Lamb Lane junction.
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Two ambulances and an ambulance officer attended the incident, with one patient being transported to Queen Elizabeth Hospital in King's Lynn for further treatment.
Two fire crews also attended the scene and helped rescue one of the people involved.
The road has since reopened.
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