An air force helicopter hoists a car from the Mohaka River, in northern Hawke's Bay, after it plunged down a cliff, killing three Mongrel Mob gang members inside.

Mongrel Mob member Ronald Rigby had methamphetamine in his blood and was trying to prevent another car overtaking when he drove himself and three other gang members off a 125-metre cliff near Wairoa, a coroner has found.

Rigby, 53, Nathan Isaac, 29, and Terry Stone, 31, died when the Honda Inspire they were in left the road and plunged into the Mohaka River, 40km south of Wairoa, on November 7 last year.

A fourth man in the car, Anthony Atkinson, miraculously survived.

MARTY SHARPE/ FAIRFAX NZ An Air Force helicopter hoists the wreck of a white Honda from the Mohaka River in 2015 after it went over a cliff, killing three of the four Mongrel Mob gang members inside.

The men had been on their way to the gang's 50th anniversary celebrations in Hastings. They had passed through the small settlement of Raupunga and the car was making its way up an incline out of the river gorge about 2.45pm when another car travelling in the same direction, a Honda Prelude, attempted to pass it on a gentle left-hand bend.

READ MORE:

* Mongrel Mob renege on funeral promise

* Mongrel Mob crash survivor forced to dog-paddle to safety

* Police find car linked with fatal crash

* Dead, missing in Hawke's Bay crash

Police located the Prelude in Raupunga days later but have not been able to establish who drove it at the time. The men who police believe were in the car have told police they received legal advice not to make a statement.

SUPPLIED Ronald Rigby had three passengers in the car he was driving from Wairoa to Hastings when it plunged off a cliff on November 7, 2015.

Coroner Chris Devonport has released the findings of his inquest into the crash. Autopsies revealed Rigby had methamphetamine in his blood at the time.

In his findings, Devonport quotes the forensic toxicologist as saying methamphetamine adversely affected drivers by making them overconfident and prone to "taking unnecessary risks, aggressive and dangerous driving and impaired ability to react appropriately".

Devonport also said a crash investigation had showed the Inspire had crossed the centreline as the Prelude attempted to overtake.

SUPPLIED Nathan Isaac, who died in the crash.

Marks on both cars showed they made contact before the Prelude braked heavily, then stopped as it hit the barrier on the northbound side of the road at the edge of the cliff.

When the Prelude stopped, the Inspire crossed in front of it, hitting the barrier at speed before mounting it and flying over the top.

The car touched the ground briefly on the other side of the barrier before it flew off the near vertical cliff.

Supplied Terry Stone, one of four Mongrel Mob members in the car

There were no witnesses and the Prelude left the scene.

Atkinson was found alive on the bank of the river at the bottom of the cliff wearing just a pair of jeans. He had a graze on his face, some bruises to his left arm and he was capable of walking and talking.

He told police that Rigby, who was driving the Inspire, had "just lost control and we went over". He said he did not see any other cars and did not think another car was involved.

MARTY SHARPE/FAIRFAX NZ The wreck of the Honda Inspire after being pulled from the Mohaka River.

Atkinson, who had been in the front passenger's seat, appeared to have been the only one wearing a seatbelt.

Stone, Rigby and Isaac died from their injuries.

Court records showed Rigby was the father of at least two children, and had made efforts to leave the Mongrel Mob and turn his life around.

MARTY SHARPE/ FAIRFAX NZ The point at which a car carrying four men began its descent of 125metres down to the Mohaka River.

He was jailed along with Stone for being part of an organised criminal group after he turned up to a 2010 gunfight at the mob's Wairoa gang pad.

Rigby had turned up to help the gang's then-president - whose patch had been stolen in a leadership quarrel - but then drove away.

He surrendered his gang patch and wrote to a judge saying he wished to turn his life around. At that point, Rigby had not received a violence convictions since 1992.