It happened on the Western Bypass on the northbound side of the road between junction 64 at Washington and junction 65 at Birtley.
The crash is said to have involved a number of cars.
The NE Traffic News account tweeted: "A1 Western Bypass, delays and one lane blocked northbound between J64 Washington to J65 Birtley due to a multi vehicle RTC emergency services travelling to the scene."
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It is not yet known if anyone has been injured in the incident.