Jack Pink, 19, and his sisters Marina, 17, and Destiny, 15, were killed instantly in a crash about 30 kilometres south of the NSW town of Boggabilla, near the Queensland border, about 6am on Monday.

Marina would have turned 18 on Tuesday.

The seven Pink children and their parents are part of a well-known, fifth-generation family working on the travelling show circuit.

They had been driving home to Brisbane after working at the annual Dubbo Show over the weekend, providing drink vans and food stalls through the family company Pink Event Catering.

On Tuesday, NSW Police released further details about how the fatalities occurred.

Jack Pink, who was driving a pantech truck and towing a food cart, crashed head-on with a fuel tanker travelling south on the Newell Highway at Boggabilla.

It appears the tanker then rolled onto a Land Cruiser 4WD towing a coffee cart and driven by Marina, with Destiny as a passenger, police believe. The tanker then exploded into flames.

Their father, Glenn Pink, was driving ahead in another vehicle and heard of the accident on two-way radio, the Boggabilla Rural Fire Service said.

He returned to the crash site and was found collapsed on the road.

The teenagers' mother, Jaze Pink, wrote a lengthy Facebook post on Tuesday wishing a happy birthday to Marina.

She said her daughter would have become a member of the Showmans Guild of Australasia today.

"You would have had an awesome leader in your midst. A flamboyant representative at your festival, show, in your town shopping and drinking!" she posted.

"Please go buy Marina Pink a drink in every GOOD bar of every town in every city, cause you guys all missed out over seas she only gave special ones her presence!

"Marina my darling as bossy as hell! Party with your brother and sister drink with the gods poppa max and prickly pink and all of our loves."

She said Marina was born when the family were on their "customary pilgrimage" north, to a run of agricultural shows 18 years ago.

She said Marina was her "exercise buddy, my breakfast maker, my canteen girl, my office girl, my head of staff, my put that back mum you don't need it girl, my don't give them what they want mum, my organise our trips girl, my listen to dad and make mum think we are listening to her, my keep Jack on his toes, my Destiny lecture giver, my kids bossy sister, but Coral and Jeanna could pull rank."

Jack's girlfriend, Monica Watkins, also posted a tribute to her boyfriend, revealing that her last words to him were "drive safe".

"I've never been so sure about someone in my life, not only did I just lose my boyfriend today but I lost my future," she said.

She had spoken to him on Sunday, saying: "I love you so much, goodnight and drive safe tomorrow".

Marina had run her own coffee cart at shows around Australia while her family ran food stalls.

A GoFundMe page has been set up to support Jaze and Glenn Pink and surviving siblings Coral, Jeanna, George and Patrick. The page had raised more than $70,000 by Tuesday morning.

Showmans Guild of Australasia vice-president Broderick Pavier said the show community was in deep shock.

"They were young kids with their whole lives in front of them," he said. "As you can imagine, we're all pretty close. This will have a huge impact across our community."

The 32-year-old driver of the fuel tanker was treated at the scene by NSW Ambulance paramedics before being taken to Goondiwindi Hospital.

He was later airlifted to Toowoomba Hospital suffering shoulder injuries.