Emergency services were called to the crash, between Pokuru and Tirohanga Rds, Tirohanga in Kinleith between Rotorua and Taupo, at 10.52am today.
Motorists are advised to avoid the area.
Diversions are being set up at Tirohapa and Poihipi Rds, as well as Tirohanga and Tram Rds.
Meanwhile, three young children have been injured and a woman is fighting for her life after a major crash between a car and a truck south of Matamata.
Two adults and the three children, aged eight months old, 2 and 3 years old, were in a car that collided with a truck carrying frozen goods at the intersection of State Highways 27 and 29, in the Waikato, at 9.45am.
Firefighters had to cut two people free from the wreckage.
The female driver suffered the worst injuries, Waikato police Senior Sergeant Simon Cherry said.
She was stabilised at the scene and flown by helicopter to Waikato Hospital in a critical condition.
The male passenger was seriously injured and three children had serious to moderate injuries. They were also taken to Waikato Hospital.
Cherry could not confirm if the adults were the children's parents.
The truck driver was not injured.
The Serious Crash Unit was investigating the cause of the crash.
Cordons in the area would remain for the next two to three hours, Cherry said.
In Bulls a woman had to be cut from her vehicle after a three car-crash on Rangitikei River bridge.
The crash initially blocked State Highway 1 south of the township, on the bridge near Tangimoana Rd, but the northbound lane has now reopened. The southbound lane is expected to open soon.
A police spokeswoman said the woman, whose car crashed into a barrier on the bridge, was the only person injured in the crash.
She has suffered serious injuries and has been taken to Palmerston North Hospital by St John Ambulance.
Meanwhile, traffic is beginning to mount on roads out of Auckland as Kiwis start their pilgrimage to baches and campsites.
NZTA advised motorists travelling north that State Highway 1 between Puhoi and Wellsford would be heavy from 7.30am through to 5pm today. And for those travelling south the heaviest time will be between 7.30am and 2.30pm.
The NZTA travel map shows traffic is heavy between Manurewa and Papakura on SH1 and between Puhoi to Wellsford.
The Tirohanga fatal crash takes this year's road toll to 102 - up from 86 at the same time last year and a 56 per cent increase from 2013.
A woman died in hospital last night after being hit by a car in South Auckland.
She was hit shortly after 7am yesterday morning in Idlewild Ave, Mangere, and died in hospital at 8.30pm last night.
In Northland, idiot drivers will be under extra scrutiny this Easter weekend, as police call on motorists to report dangerous driving during the expected surge of traffic on the region's roads.
Inspector Wayne Ewers said more staff and the booze bus would be on the roads over the weekend, and police expected Thursday, Friday and Monday to be the busiest days.
Police from the Waitemata Police District would also patrol into Northland, as far north as the Ruakaka roundabout.
Yesterday, Auckland motorways were clogged as people fled the city heading north and south.
Associate Transport Minister Julie Anne Genter said it was her "top priority" to stop so many New Zealanders dying on the roads.
"I urge people to take care on the roads this Easter Weekend, and to drive responsibly," she said.
"We know that the vast majority of serious crashes result from simple mistakes on the road.
"This highlights the importance of driving fresh and not taking risks, as well as the need for the Government to do its bit to make our roads safer."
AS PREDICTED: Traffic is heavy on SH1 northbound between Puhoi to Wellsford. Road users are advised to expect delays and allow extra time for their journeys when travelling through this area. For more information on predicted busy periods visit: https://t.co/niBHpHed7k. ^MF pic.twitter.com/g39emOu1fs
— Waka Kotahi NZTA Auckland & Northland (@WakaKotahiAkNth) March 29, 2018