With State Highway 1 still closed at Mangamuka Gorge by slips triggered by the July storm, Kaitaia-Awaroa Rd is currently the main west coast route to Kaitaia.
Kaitaia traffic is being diverted through Waiotehue Rd, a winding, unsealed back road.
Motorists are advised to avoid the area.
Two St John Ambulances responded along with the Whangārei-based Northland Rescue Helicopter. A Westpac helicopter was also sent from Auckland.
A St John spokeswoman said one of the patients was in a serious condition.
The second patient is being treated at the scene and does not require hospital treatment.
The seriously injured patient was flown to Whangārei Hospital about 2pm.
Volunteer firefighters from the Kaitaia and Ahipara brigades are also at the scene, along with a crash investigator from the police Serious Crash Unit.