Inspector Jeff Penno says police are "gutted" about the horror crash south of Hamilton in which the American trio died.

A holiday of a lifetime has turned to tragedy for two American couples after three of them were killed in a collision with a truck enroute to visit the Mormon settlement south of Hamilton.

Utah woman Ruth-Ann, 49, and her husband Mitchell Peterson, 50, from Monroe, died in the crash along with Tamara Garlick Barnett from Richfield, in the US state of Utah, police said.

Barnett's husband Richard Barnett, 56, was taken to Waikato Hospital with moderate injuries and is in a stable condition in a ward.

Facebook Ruth Ann and Mitchell Peterson died in a fatal crash south of Hamilton.

The two couples had arrived in New Zealand a few days ago and had been travelling back from Waitomo Caves to visit the temple at the Church of Latter-Day Saints at Temple View.

Police said the quartet had rented a Toyota Highlander and were heading north when they turned right onto Tuhikaramea Rd into the path of an oncoming truck and trailer unit heading south towards Pirongia.

The three were passengers in the car and died at the scene while the driver was taken to hospital. The truck driver had escaped uninjured but had been left shaken by the ordeal.

SUPPLIED/FACEBOOK Tamara Garlick Barnett died in the crash and her husband Richard suffered injuries.

Family of the Barnetts had started a fundraising page to help aid in Richard's recovery at Waikato Hospital and pay for funeral costs for Tamara, who was known as Tammy.

"Our dearest wife, mother, daughter, sister, aunt, grandmother and friend Tammy tragically left us while on the trip of a lifetime to New Zealand with her beloved husband Richard. Tammy had an incredible energy about her and will be sorely missed."

Both couples were prominent, well-known members of the Church of Latter Day Saints in the settlement of Richfield, and nearby Monroe, about 2.5 hours from Salt Lake City.

Mark Taylor CLOSED OFF: A police cordon at Ngahinapouri, scene of a fatal crash where three people died.

Ronald Hawkins, director of the church's Temple View visitor's centre in Hamilton, said New Zealand's arm of the church had been in contact with Richfield.

He had been informed of the fatalities this morning and said the church community had rallied to provide any support possible to the injured man and family overseas.

"It is always a tragic situation when you loose loved ones. I understand they had young children and the family at home will be missing them tremendously. It will be a huge shock for that community."

Elder Hawkins, who is from Utah originally, did not know the group personally but understood they were members of the tight-knit Mormon community in the 20,000-strong population of Richfield.

The Hamilton temple was the only one of its kind in NZ and was regularly visited by church members from America, he said.

"We have temples throughout the world, they are a very sacred place and in this situation would bind families together. It is ironic they were coming here at the time they lost their lives...but we are reassured that families will be together, they are an eternal unit, and will look forward to resurrection."

Dr Barnett was an orthodontist and director of Barnett Orthodontics in Richfield, and together the couple have four children and four grandchildren. Mitchell Peterson was also a doctor in Richfield, practising optometrist.

Acting Waikato District Road Policing Manager Jeff Penno said police were "absolutely gutted" that another crash had claimed three lives, bringing the Waikato road toll this year to 13.

"This is an absolute tragedy," Penno said.

"Those people were tourists to our country and we live in the most beautiful country in the world so its only natural people want to travel here but that brings a whole pile of challenges with it."

He said the four in the car were all wearing seatbelts and it wasn't a case of pointing the finger at tourists.

"We are gutted, we are out there everyday working to make the road as safe as we can and this is disappointing. These are families, these are lives, the heartache and pain is indescribable."

He said police work with partner agencies to try and ensure the road is safe, speed limits are in place, road conditions and vehicles are up to scratch.

"We except people make mistakes, we accept we are human but at the same time the roading system should be designed... to compensate those mistakes."

He urged against any vigilante action by motorists, who should call *555 with driver complaints. The crash, at the intersection on SH39 and Tuhikaramea Rd near Ngahinapouri, was not a 'blackspot' but was a high traffic area, said Penno.

"Conditions at the time were overcast and the road was reasonably dry."

Gilmour Road residents, a few hundred metres down from the crash site, said the stretch of road where the accident happened was dangerous.

"The intersection [where the crash happened] is dodgy," one said.

"Trucks come over the hill without you seeing it and you just don't have time to come out of the intersection safely if you're speeding.

"It would make a difference I think if they lowered the speed level down here to 80kmh."

A police officer who was first on the scene had provided first aid until paramedics arrived, but the three victims had died at the scene.

Penno said Waikato police were working with the local church and consular officials to provide support.

Thoughts also went out to the rescue staff "who worked hard under trying conditions" to deal with the aftermath, said Penno.

Last month a family of four United States citizens living in Hong Kong died when the car they were in collided with a logging truck north of Tokoroa. Warren Lee, 53, Aesoon Lee, 52, and their daughter 20-year-old Julia Lee died at the scene. Their son, Griffin Lee, 17, died later in hospital.

The family were travelling in a car heading north on State Highway 1, which crossed the centre line and hit a logging truck travelling south.

The family had come to New Zealand to settle their daughter - who had been living in Massachusetts - into university in Aucklander. Her 18-year-old brother, Griffin Lee, also a United States citizen living in Hong Kong, survived the crash but later died in Waikato Hospital.

Julia Lee was driving the car when it crashed, while her parents were in the back seat and not wearing seatbelts, police said.