NZTA has warned motorists to allow at least 90 minutes for the detour.
"The road is expected to be closed for some time so people should avoid the area if they can or check before they travel."
The Serious Crash Unit and the Commercial Vehicle Safety Team have been advised.
The incident follows another fatal crash in the Bay of Plenty this morning, where one person was killed.
Emergency services were called to Tirohanga, between Pokuru and Tirohanga Rds, at 10.52am.
Diversions were initially set up, but the road reopened around 4.20pm.
Meanwhile, three children, including an 8-month-old baby and a 3-year-old boy, 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 three children were in a car that collided with a truck carrying frozen goods at the intersection of State Highways 27 and 29, Waikato, at 9.45am.
Firefighters had to cut two people free from the wreckage.
The female driver suffered the worst injuries, Waikato Senior Sergeant Simon Cherry said.
She was flown to Waikato Hospital in a critical condition.
The male passenger was seriously injured and the three children had serious to moderate injuries. They were also taken to Waikato Hospital.
The truck driver was not injured.
The Serious Crash Unit was investigating.
The Tirohanga fatal crash takes this year's road toll to 103 - up from 87 at the same time last year.
A woman also died in hospital last night after being hit by a car in South Auckland.
She was hit shortly after 7am yesterday in Idlewild Ave, Mangere, and died in hospital at 8.30pm last night.
The Serious Crash Unit is investigating.
