Meanwhile, emergency services also attended the scene following a crash at the Neilson St off-ramp, NZTA advised.
A Hato Hone St John spokesperson said one rapid response unit attended shortly after 7am but was not required.
The off-ramp had partially closed following the crash, but in an update NZTA said it had since been cleared.
However, the highway remained closed due to the large slip and fallen tree.
“Please pass with extra care and expect delays,” the agency warned.
There is a detour in place and motorists are being asked to allow extra time for travel.