The multiple-vehicle crash happened at 9am near the Bowburn junction and Coxhoe.
The North East Ambulance Service sent four ambulances to the scene and five people were taken to Darlington Memorial Hospital for treatment.
The southbound carriageway between junction 60 and 61 is still closed.
A spokesperson for North East Ambulance Service said: “We were called to a multi-vehicle road traffic incident on the A1 at Coxhoe at 9am this morning.
“We dispatched four double crewed ambulances, a duty officer and a commander to the scene.
“Five patients were taken to Darlington Memorial Hospital.”
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A National Highways spokesperson said: “Due to a road traffic collision southbound on the A1M between J61 Bowburn and J60 Chilton the carriageway is currently closed.
“Emergency services are on scene and there are no delays reported on the approach.”
We have contacted Durham Police for more information.