Less than an hour after the crash, a motorcyclist was killed on State Highway 5 after colliding with a car.
The motorcyclist died at the scene on the Napier side of the Te Haroto Hill about 3.30pm.
Police were still working to identify the victim last night.
The Mongrel Mob group was heading from Wairoa to Hastings to attend the gang's 50th birthday celebrations.
It is understood they had stopped on the side of the road at the scene of a previous fatal crash which had claimed the life of a gang member, and their car was struck by another vehicle about 2.40pm.
Police were not able to confirm that when contacted by the Herald on Sunday last night.
Emergency services responding to the crash were joined by Mohaka locals who also rushed to the scene, including orchard worker Sam Evans.
"Somebody came in from the road, into the orchard, and asked if anybody had a boat," he told the Herald on Sunday last night.
"I'm a keen kayaker so I just grabbed my kayak and headed down to the river to see if there was anything I could do. I ended up seeing a vehicle in front of me in the river."
Evans helped emergency service workers carry the survivor into the Lowe Corporation Rescue Helicopter, which airlifted him 150m up to the roadside.
Police divers last night travelled to Wairoa to begin a search of the Mohaka River to find the missing men, who are believed to be trapped inside the car.
"The police dive squad will begin a search for them when they arrive at the scene," a police spokesman said.
Police knew the identity of all four men but did not release their names last night.
The road toll for the year stood at 270 yesterday - way ahead of the 243 who had died on the roads by the same time last year.
