Multiple crashes in the upper North Island closed State Highway 2 in several locations, and blocked SH25 north of Thames and SH27 in Waikato.
Traffic is flowig freely again on State Highway 27, after it was blocked by a two car crash at Kaihere in Waikato this evening.
One person was flown to hospital by emergency helicopter in a serious condition.
State Highway 25 remains closed after a crash involving a campervan and car. One person had to be extracted from the car.
The highway is closed, and no alternative routes are in place.
The road will be reopened once the scene has been made safe, police said.
At least 11 people were treated for injuries earlier today after two cars collided near the intersection of SH2 and SH1 at Bombay.
The vehicles crashed head on about 2.40pm, and several passengers were transported to hospital, police said.
SH2 was closed near the intersection and also in Opotiki, where three cars collided. The highway has since reopened.
In Opotiki, five people were injured after an SUV appeared to lose control on a bend, crashing into two oncoming cars, Tauranga based Trustpower TECT Rescue helicopter said.
One of the drivers - a 63-year-old Rotorua man - suffered critical head injuries. He was stabilised by St Johns paramedics before being flown to Tauranga Hospital in a critical condition.
Traffic is being diverted on SH2 from Parata Ridge Road.
Further north, long delays followed a serious crash near Mangatawhiri between Pokeno and Maramarua.
Police urged motorists travelling to Auckland from Coromandel or Bay of Plenty to delay their travel, or use alternate routes.