Update: A 16-year-old boy has been charged over the crash.
Two girls aged 14 and 15 were killed when the car they were in left the road and smashed into a tree next to the Monaro Highway on Saturday night.
They were passengers in the car which was so badly damaged officers initially couldn't identify the make of it.
Two teenage boys who were in the car, one of them the driver, are thought to have fled the scene but been identified by police later.
"Police located them at residences a short time later.
"They have received medical attention and are currently assisting investigators from the Major Collision Team with their inquiries," an ACT Policing statement said.
"A Toyota sedan had left the roadway, crashed through a row of temporary fencing and then collided with a tree.
"Two teenage girls aged 14 and 15 were found in the vehicle and they were declared deceased at the scene."
Officers were first called to the scene in Hume, just south of the Lanyon Drive intersection, at about 8am on Sunday when they found the two girls dead in the car.
It's not known, though, exactly when the crash happened.
It may have been that the car left the road in the torrential rain late on Saturday night and then stayed at the side of the road until a member of the public called the police around dawn on Sunday.
Detectives were interviewing the two male teens from the crash.
Officers were not saying what the possible theories were but one is thought to be that the four teenagers were on a late night "joy ride" which turned to tragedy.
There was torrential rain on Saturday night.
The two teenage passengers were thought to have died some time before police and ambulance crews arrived at the scene.
Acting Detective Inspector Brian Tadic said the impact was "severe so speed might have been a factor".
The northbound lane of the Monaro Highway was closed for most of Sunday.
The crash takes the number of road deaths in the ACT this year to 14, compared with 11 for all of last year.
Two weeks ago, a 19-year-old woman died after being hit by a car while riding an electric scooter outside the Namadgi School in Kambah.
The rider of the scooter had been "thrown a substantial distance across the intersection" and she was not wearing a helmet.
And on August 29, two vehicles crashed head-on on Sulwood Drive in Kambah.
The 42-year-old driver of a Volkswagen was trapped in the vehicle but died at the scene. The woman driving the other car, a four-wheel-drive, was taken to hospital with minor injuries.
The reason for the rise in the number of fatalities isn't clear. There were lockdowns last year and that may have kept people off the roads. The rain - with the bad driving conditions - has also been relentless this year.
Police asked anyone who might have information about the latest crash to contact them.
"Anyone who witnessed the car leave the road or who drove past the collision site and saw the vehicle prior to 8.00am on Sunday is urged to contact Crime Stoppers on 1800 333 000, or via the Crime Stoppers ACT website. Please quote P2107669," a police statement said.
"ACT Policing urges all road users to slow down and drive to the conditions."
