Tributes have flowed for the four men, who died when their car became airborne, ploughed into a tree and was severed in two on the Northern Highway on Wednesday.

The men, aged between 19 and 28, were from Echuca, Moama and Craigieburn.

One of the victims, Chris Reddin, a 22-year-old father of a baby boy, was among those killed.

Grieving relatives said he was a "beautiful person" who would be deeply missed.

"He was always so good to me, and always so loving to everyone," said Jayden Reddin.

"There are a lot of people who are extremely sad today ... crying and devastated," he said. "This is something we will have to try and get through together."

Three other victims of the fatal crash have been identified as Joshua Taylor, Nick Mongta and Corey Bray.

Another relative of one of the victims, who did not want to be named, said that Mr Reddin, Mr Taylor and Mr Mongta were former students of Echuca College, who were outgoing, charismatic and "loved hanging out with their mates".

It is understood their silver sedan hit a wire rope barrier, rolled and then crashed into the tree off the highway near Halpin Court, just south of Pyalong.

The impact of the crash bent the car in two.

Speaking at the site of the crash, road policing assistant commissioner Robert Hill said the "horrific" scene was one of the worst he had encountered in his years in the field.

"It is a shocking sight, it is a shocking scene ... it is something that certainly will stay with me for some time," he said.

Mr Hill said initial investigations indicated the car was travelling north when the driver failed to negotiate a left bend in the road about 6.30am on Wednesday.

"For one reason or another that vehicle has careened to the right-hand side and travelled off the road ... has struck a wire road barrier, or the commencement of a wire rope barrier, has then travelled airborne some distance and then has crashed into a tree after rolling," he said.

"The roof of the vehicle has actually struck the tree."

No one saw the crash, but some people have reported hearing it unfold to police.

Mr Hill confirmed a P-plate was found nearby.

"We're looking at usual factors that include fatigue, alcohol, or drugs, that would have caused this crash."

Mr Hill was in the same part of the state 12 months ago, after four other people were killed in tragic circumstances.

"Yet again we've seen four people lose their lives in circumstances that could have been avoided," he said.

"We have four families now that will be grieving, grieving today, tomorrow and for their lifetime."

Halpin Court resident Rosa Bazzano said her neighbour, who was new to the area, had happened upon the crash scene on her way to work.

"She's the one who rang triple-0," she said.

Another resident Moira Waye said she did not realise the crash had occurred until she heard the sirens of the fire trucks.

"I didn't hear anything until the fire trucks arrived," she said.

"I don't know whether they were locals. Obviously, because it's a busy road, it could have been anyone travelling north."

Detectives from the Major Collision Investigation Unit will investigate the circumstances surrounding the crash.

A section of the Northern Highway surrounding the crash, between Broadford-Pyalong Road and Seymour-Tooborac Road, was closed for several hours but reopened shortly after 5.30pm.

Horrific image from the #9News chopper of fatal crash at #Pyalong. Car up a tree and split in half @9NewsMelb pic.twitter.com/VvvPYnUDuM — Laura Spurway (@laura_spurway) January 27, 2015

A quadruple fatal has occurred on a highway north of Melbourne, with a car hitting a tree. Updates to come. #9News pic.twitter.com/ea27XJCd7B — Nine News Australia (@9NewsAUS) January 27, 2015

More to come.