Emergency services at the scene of the fatal accident on the Mohaka Bridge, Hawke's Bay.

A mystery blue car could have been involved in a crash that sent a carload of gang members plunging to their deaths.

Police are hunting sightings of the car after three people died and one man escaped without serious injury when their car plunged 150 metres down a steep cliff and into the river near the Mohaka Viaduct, north of Hastings, on Saturday night.

Reportedly, Police said they suspect a blue Japanese-make car with a dent on its bonnet might have been involved in the crash.

MARTY SHARPE/ FAIRFAX NZ The car plunged 150m down a sheer cliff.

It is understood the Gisborne criminal investigation bureau is exploring the possibility the men were run off the road.

Authorities had granted a liquor licence for the Mongrel Mob party the men were headed for that night in the paddock behind Te Aute Tavern, despite police warning it would attract drunken violence.

But as the 50th anniversary bash got underway, police arrived for a different reason.

MARTY SHARPE/ FAIRFAX NZ Police examine the barrier where the car crashed before plunging down the cliff.

They quietly pulled several gang members aside and broke the news of the tragedy to them, tavern owner Ian Morse said.

"It was sad. Some of the members left. They wanted to get away to support the families and that. Other than that everyone was pretty unaware and it was a good night."

"Not everyone was told initially - just the people that were affected personally. They didn't want to ruin the rest of the party totally."

The revellers drank until about 1.30am Sunday and were packed up by 2am.

Despite the initial reservations about the gang event, no arrests were made, and they fielded no complaints from the public about the gathering, police said.

Meanwhile, police divers retrieved two more bodies trapped in the submerged car's wreckage on Saturday night and Sunday.

Detective senior sergeant Brent Greville said no witnesses had seen another vehicle but it was something police were looking into.

"There may be a possibility that another car was involved. It's an aspect we need to look into as part of the investigation so we would like to talk to anyone who may have seen anything unusual on that section of the highway during that time."

Police said last night they would not release the names of the car's occupants yet.

One of the men believed to have died in the crash was jailed for four years and three months in 2010 for participating in an organised criminal group after two warring gang factions held a shoot-out over an argument about who should be the gang's top dog in Wairoa.

Greville appealed for any witnesses to come forward who may have seen the crash or noticed any other vehicles on the stretch of road near the top of the hill near the approach to the viaduct around 2.30pm on Saturday.

The road near the viaduct was scheduled to be closed for two hours on Sunday night so emergency crews could fish the car's wreck out of the water, while police continued to probe the cause of the crash.

They had yet to formally identify the two men pulled from the wreckage and were still informing families of the deaths.