Several ambulances were called to the northbound carriageway on the A19 near Seaham at 4.30pm today.
The North East Ambulance Service confirmed they took three people to Sunderland Royal Hospital following the incident.
Several vehicles were believed to have been involved in the accident and there were delays for motorists.
It is not known at this stage how serious the injuries were.
The collision has happened between Herrington Interchange and the Seaham turn off, with congestion back to the Durham Lane junction.
Traffic from Peterlee towards Sunderland is being affected.