A crash on Auckland’s Northern Motorway is causing a traffic backlog this afternoon.

Waka Kotahi NZ Transport Agency posted to social media explaining the crash was blocking the two right southbound lanes between Tristram Ave and Northcote Rd on State Highway 1.

All lanes reopened around 3.40pm, just under an hour after the initial crash at 2.40pm, but Waka Kotahi warned there would be residual delays.

The crash has left one person with moderate injuries, a Hato Hone St John said, and they have since been transported to hospital.

According to Google Maps, traffic was backed up for nearly 4km and it was taking commuters 21 minutes to complete the stretch of road.

Traffic is backed up for nearly 4km. Image / Google

Pictures posted by Waka Kotahi show police and Fire and Emergency attending the scene of the crash.