Drivers are stuck in traffic queues for up to an hour after the A1(M) was closed northbound due to a gas leak from a tanker.
The motorway has been shut between junction 63 for Chester-le-Street and junction 64 for Washington after a broken down tanker was found to be leaking hydrogen.
Highways England says the vehicle contains nine cylinders of the gas, one of which has a crack and is leaking, and the only safe way to deal with it is to let it vent. Follow live updates here.
Emergency services on the scene also believe the other eight cylinders have been affected and they will also need to vent, which will take several hours.
The tanker can’t be moved while the gas is venting due to the fire risk from the flammable hydrogen.
An exclusion zone has had to be set up around firefighters who are working at the scene and specialist engineers have also been called to the tanker.
Originally the entry slip road onto the A1(M) was closed but the entire carriageway was shut down from 4am on Thursday.
Diversions are in place using the A167, Vigo Lane and the A195, however, there are heavy delays on the A1 approaching the closure and on the diversion route.
Tailbacks on the A1 are stretching back for around three miles and drivers have been urged to find alternative routes.
Durham Constabulary has said that the road is expected to stay closed for most of the day.
Southbound traffic has not been affected and the road remains open.
