A photo tweeted by NZTA shows traffic banked up. Motorists are being warned to expect delays.
Meanwhile in Mission Bay, one person was seriously hurt when they were struck by a car on Kepa Rd at about 6.50am, a police spokeswoman said.
Another person was critically hurt south of Auckland in Glenbrook in a two-car crash at about 5.30am.
The crash took place at the intersection of Glenbrook-Waiuku and Mission Bush Rds, trapping one person.
The trapped driver was taken to hospital in a critical condition, a police spokeswoman said.
Another person involved in the crash was taken to hospital with moderate injuries.
Police asked motorists to avoid the area as serious crash investigators examine the scene.