A fiery car crash that killed three teenagers in Melbourne's north is likely to have been a freak accident, police say, triggered by the driver losing control as the tyres spun out on the wet suburban road.

Witnesses spotted the Mercedes-Benz sedan fishtailing as it pulled out of a side street on Thursday afternoon and on to Westgarth Street in Northcote.

But within seconds the car left the road, struck a parked car, a tree, and then became wedged between a brick wall and a power pole, trapping everyone inside.

The fuel tank had also ruptured and ignited, incinerating the occupants almost instantaneously.

Police believe the fire may have been started by a spark from the car battery or heat off the engine as it came into contact with the spilt fuel.

The blaze was so intense it took a day for police to confirm there were only three teenagers killed inside the wreckage and not four - the driver and two of his 18-year-old friends.

Flowers have been placed at the crash site on Friday as a tribute to the dead teenagers.

Inspector Steve Smith said police aren't sure if the driver had intentionally spun the tyres, or if he was swerving to avoid something on the road, losing traction in the rain.

It's believed the P-plater was speeding at the time but only just over the limit, he said, but investigators have ruled out alcohol as a contributing factor.

"It's terrible accident, quite a horrific scene, and it's very unusual to have an accident of this severity in a quiet suburban street," Insp Smith told reporters on Friday.

"It's very, very rare and it was a terrible scene for the emergency workers, but also for the residents."

The three bodies may not be formally identified for weeks as police turn to dental records and DNA testing to confirm who they believe was killed in the wreckage.

Family members have been notified about who could have died in the crash.

An aunt of the suspected driver is now remembering him as a fun-loving man.

"I will miss and think of him every day," she said in an email to Fairfax Radio.

"Thank goodness I have so many memories, mostly wonderful."

The crash came during a devastating 24 hours on Victoria's roads that also saw two others lose their lives in separate crashes.

Superintendent Neville Taylor said the series of crashes push the state's road toll up to 107, three more than at this point last year.

"It is a good, strong reminder to us all that this can all change so quickly and so easily," he said.

"Road trauma is not something that any of us can be complacent about."