Four teenagers were in the Volkswagen sedan which collided with a truck at the intersection of Somerton Road and Dennis Street in Somerton about 3.35am.

The 17-year-old driver and one of his passengers suffered life-threatening head injuries. One was taken to The Alfred hospital, while the other was taken to the Royal Melbourne.

Detective Sergeant David Newman told radio station 3AW it appeared the car was travelling at "excessive speed" when it ran a red light, crossing the path of the 23-tonne truck.

"The truck has T-boned the car," he said.

"The impact was that great it's actually tipped the truck on its side. It's a horrific scene.

"[With] the speed and the impact with the truck of that size [the car] is a mess. It was trapped underneath the truck.

"It has been a massive impact. Combine high speed with a truck ... it's always going to have tragic consequences."

It is believed the car was travelling at up to 150km/h in the 80km/h zone.

All four male teenagers, believed to be aged 17 and 18, needed to be cut from the car.

One was trapped for more than an hour in the wreckage, an Ambulance Victoria spokesman said.

He was taken to the Royal Melbourne Hospital with serious leg injuries.

The fourth teenager was taken to the Royal Melbourne with serious head and chest injuries.

One of the four injured was 17-year-old Jose Paulete, who was sitting in the passenger seat behind the driver at the time and is now in a stable condition in the Royal Melbourne Hospital.

"I've got a broken nose, broken spine, broken hips and a fractured skull," he told Channel Nine from his hospital bed.

Sergeant Newman said there were a "couple of witnesses" to the crash, who had been interviewed by police.

"The truck driver stopped at the scene and is speaking with police," a police spokeswoman said.

The truck driver, believed to be aged in his 20s, escaped serious injury but was assessed at the scene by paramedics.

Detectives with the major collision investigation unit are working to determine the cause of the crash.

Drivers have been urged to avoid the area, as the intersection is expected to be blocked for some time.

Anyone with any information can contact Crime Stoppers on 1800 333 000.

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