State Highway 25 has been closed at Pukepoto in the Coromandel after a vehicle crashed into a power pole, bringing lines down onto the road.
Police say the accident happened between Timata Road and Woody Hill Road around midday on Saturday.
"One of the occupants received serious injuries and another, who had to be extricated, has been critically injured," a police spokesperson said.
The highway will remain closed for some time while the serious crash unit investigates. State Highway 25 is also closed between Coromandel township and Matarangi due to slips.
Police say motorists should expect delays, and delay travel if possible.
