The driver of a white van had braked sharply and taken evasive action to avoid a head-on with the truck.
Two drivers following the van - one in a white Subaru and the other driving a steel grey Subaru Legacy - braked heavily to avoid nose-to-tail crashes with the van only to both be hit from behind by a Rav 4 police said had been approaching "at speed."
The names and condition of the injured people is not known although the driver of the Rav 4 received the most extensive injuries.
Mr Lee said police in South Wairarapa and Hutt Valley had been alerted in the hunt for the truck that failed to stop at the crash scene.
A description was of a green truck, not a stock carrier, which could have been a furniture mover.
Likewise the cyclist had not stopped and was being sought by police for questioning.
Later in the day, about 4pm, a crash at Waingawa closed the state highway again. Three people, including a 3-year-old boy were taken to hospital with moderate injuries.
Kyle Karaitiana is thinking of buying a Lotto ticket for Christmas after walking away from his mangled vehicle without a scratch on him.
He was waiting to turn right into Norman Ave when his car was hit from the rear by a car travelling south. His car was "flipped" into the air and pushed into oncoming traffic, slamming into a Ford Laser heading north.
"It was the scariest thing I've been in in my life."
Mr Karaitiana said he saw the accident happen in slow motion.
"I saw this car coming up behind so I tapped the brakes a few times so he'd see my brake lights. He just kept coming ... I had nowhere to go. There were cars coming the other way."
The crash saw diversions in place between Clareville and Taratahi.
Constable Rod Gully said police were still investigating but it appeared a car travelling south had hit Mr Karaitiana's car as he waited to turn right, pushing his car into the path of oncoming traffic.
After looking at Mr Karaitiana's car, Mr Gully said a car seat probably saved the 3-year-old's life.
"From what I've seen I'd say that car seat physically saved his life."
He warns motorists to watch following distances to avoid a tragedy in this festive season.