Six people are in hospital and one may have died after a petrol tanker rolled, crushing a car and starting a chain of collisions on a Melbourne motorway.

Most of the six have neck, shoulder and facial injuries and are in a stable condition in hospital following the smash this morning on the Calder Freeway in Keilor East.

Two other people were assessed at the scene and didn't go to hospital, Ambulance Victoria says.

Scene pictures show a car flattened, another on its roof and a long line of cars that have crashed.


The flattened car has been covered with a blue blanket. Emergency services are yet to confirm how many people are inside.

Victoria Police are not confirming any deaths but reports suggest one person may have been killed.

Witnesses on Facebook said the scene was utter chaos with people running around.

"Just saw a lady in her car pulled on the side and wiping her tears," Melissa Fry wrote on Facebook.

"I saw a girl, in the orange car, she was looked like she hit her face on the airbag. She had her handkerchief to her face, sitting in her car, with the driver's side door open," Andrew Chung told The Age.

The tanker was carrying 600 litres of diesel and 20,000 litres of unleaded petrol, which is leaking over the road.

Firefighters have covered the fuel in fire retardant foam as they work to clear the scene.

VicRoads says there are about 10 cars involved and the freeway will remain closed well into the afternoon.

The tanker's driver was taken to Royal Melbourne Hospital in a stable condition with leg injuries.

Toll, which operates the crashed tanker, told AAP the company has activated an emergency response plan and is working closely with the authorities at the scene.