In the afternoon's most serious crash, just before 4pm, at least seven people were injured and State Highway 2 was closed near Bombay, south of Auckland.
St John was alerted to the accident at 2.36pm and sent a rescue helicopter and four ambulances to the scene.
The incident happened on State Highway 2 near Avon Rd, just east of the intersection with State Highway 1.
More than 20 people were injured, one was killed and several roads were closed after more serious car crashes today.
In the Bay of Plenty, six people were hurt, one with critical injuries, after a crash at Waiotahe this afternoon.
The patients were treated and taken to hospitals in Whakatane and Tauranga shortly before 2pm.
The crash blocked State Highway 2 west of Opotiki, police said.
At about midday, a crash in the same area saw two people transported by St John to Whakatane Hospital with serious injuries.
Another six people were injured in Westland after a car crash on State Highway 6 near Ruatapu.
St John said all six patients had minor injuries. Two ambulances were at the scene at 1.25pm.
In Northland, State Highway 1 south of Kawakawa was blocked at 12.56pm after a crash. And in Manukau, a car collided with a power pole, bringing power lines down and closing Linwood Rd in Kingseat at 1.40pm.
In the afternoon's most serious crash, just before 4pm, at least seven people were injured and State Highway 2 was closed near Bombay, south of Auckland.
A serious crash closed SH2 just east of the intersection with SH1, Bombay. Traffic diversions are in place along Koheroa Road and Island Block Roads. Photo / Auckland Westpac Rescue Helicopter Trust
St John was alerted to the accident at 2.36pm and sent the Auckland Westpac Rescue Helicopter and four ambulances to the scene.
The incident happened on State Highway 2 near Avon Rd, just east of the intersection with State Highway 1.
A spokeswoman for the Fire Service said one person was trapped during the incident and had been flown to Middlemore Hospital in a serious condition. Three others were seriously injured, a further two had moderate injuries, and one had minor injuries, a St John spokesman said.
Five of those injured were believed to be children.
Police said traffic diversions were in place along Koheroa Rd and Island Block Rd.
Heavy motor vehicle drivers were advised to use Island Block Rd or "other suitable routes".
Police urged motorists returning to Auckland from the Coromandel or Bay of Plenty to either delay their journey or use alternative routes away from the crash.
The Fire Service was called to free people trapped when a campervan and car crashed north of Thames late this afternoon.
Earlier today, one person died and two were injured when a light van crashed near Nelson at 2am.
The holiday road toll rose to eight after that accident. One of the injured people from the fatal van crash was flown to Nelson Hospital with spinal injuries.
Police said the crash happened on the Riwaka side of the Motueka River bridge.
Senior Sergeant Blair Hall said the investigation was in its early stages but it seemed the driver of the vehicle died at the scene.
Police said the other two people were taken to hospital with what appeared to be moderate to serious injuries.
"The crash does not appear have involved any other vehicles, and evidence at the scene would indicate speed was an aggravating feature leading to this crash," Mr Hall said.
The Nelson helicopter also flew two seriously injured patients to Christchurch from the major bus accident at Otira Gorge near Arthur's Pass on New Year's Eve.
The provisional road toll for all of last year is 321, the highest number since 2010.
"It's incredibly sad and disappointing to have lost so many lives on our roads in 2015," Associate Transport Minister Craig Foss said.
"The road toll is not just a number - every figure represents not only the life lost but also grieving families, friends and communities."
During the holidays a year ago, 11 people died as a result of road crashes. The highest holiday road toll was recorded in 1972/73, with 37 deaths. The lowest was three years ago, when six people died.
The Ministry of Transport's official holiday period started at 4pm on Christmas Eve and will end at 6am this Tuesday, January 5.
