The road connecting Northland with the Far North reopened to the public on Friday after a two-and-a-half-year closure.
Hato Hone St John said it sent three ambulances and a helicopter were sent to the scene, near Rangiahua Rd. One patient has been flown to Northland Base Hospital in a serious condition.
The crash was reported about 9.20am today.
New Zealand Transport Agency/Waka Kotahi said people should avoid the area and consider an alternative route.
The police serious crash unit has been advised.
A 13km stretch of highway through Mangamuka Gorge in the Far North, just south of Kaitāia, was destroyed by slips during torrential rain in August 2022.