LATEST: A truck has rolled at the entrance to Auckland's Victoria Park Tunnel injuring two people and leaving the city facing extensive gridlock.
Police said the truck appeared to have lost control coming down the Wellington St on-ramp onto the motorway and then rolled, blocking all three northbound lanes of State Highway 1.
Police were unable to give details of the injuries. No other vehicles appear to be involved.
NZTA said northbound drivers should leave SH1 as soon as it is safe for them to do so and use alternative routes.
Drivers can rejoin the motorway at Fanshawe St but quicker alternatives will be the southwestern motorway at Manukau or the northwestern motorway.
Tweets and eyewitness reports said dozens of vehicles were unable to get off the motorway and people been getting out of their cars and walking on the road.
The Automobile Association is advising that the tunnel is likely to be closed for a while and said northbound traffic should use the northwestern motorway and the upper harbour highway.
The tunnel opened to traffic in November last year.
It was designed to take the northbound lanes of the southern motorway through to the harbour bridge while the southbound lanes now run across the original Victoria Park viaduct.
- Auckland Now
Are our classrooms becoming overcrowded?