A collision that killed a 15-year-old girl has been described as "every parent's worst nightmare" with the car spotted driving erratically before the crash.
A 14-year-old girl was allegedly behind the wheel of a stolen Holden Captiva when it collided with a truck on the Hume Freeway, at Locksley in northern Victoria about 8.20am on Wednesday morning.
The 15-year-old girl was in the front passenger seat and died on impact, Victoria Police said.
A 12-year-old boy was in the back seat and taken to Melbourne's Royal Children's Hospital in a stable condition.
The teenager driving the car was flown to the Royal Children's Hospital with upper body pain and was put under police guard.
Both the 12-year-old and the 14-year-old remained at the hospital in a stable condition as of Wednesday night.
Police believe the three were friends from the Wangaratta area in Victoria's northeast.
The car they were in was taken from a driveway near Wangaratta before midnight on Tuesday, Victoria Police eastern region Superintendent Michael Layton said.
The vehicle was reported driving erratically earlier on Wednesday morning.
"This is a tragic scene and high risk-taking behaviour by youths," Supt Layton told reporters.
"It's totally avoidable ... (and) it's probably every parent's worst nightmare who might be dealing with rebellious teens and young people."
Police are yet to determine exactly what led to the crash and major collision investigators are examining the scene.
Both the car and truck were travelling in the same direction, with the truck in the left-hand lane of the freeway, Supt Layton said.
"The truck driver wasn't aware of anything prior to the impact," he said.
"He's pulled over and done his best to render some assistance.
"It was a difficult and confronting scene for him, as it was for all of our emergency services and first responders and those commuters that have stopped to try and do what they could."
The 45-year-old truck driver, Clint Sneddon, was uninjured in the crash.
He said he was driving at 99km/h when the car hit his truck hard and he was jolted.
"They were just yelling and screaming and said that the passenger died," Mr Sneddon told Nine News.
"I don't know what it is with these young kids, I don't understand what they get out of that.
"Look where it has got them. One is dead and (the other two) have got to suffer for the rest of their life and deal with it."
There would be consequences for the 14-year-old as a result of the incident, Supt Layton said.
Anyone with information about the crash or dashcam footage has been urged to contact police.
