One killed, five seriously injured in shocking smash on Melbourne freeway

A man was killed when his car was crushed in a horror Melbourne crash described by authorities as one of the worst they have seen.

The Calder Freeway is expected to stay closed in both directions through to Wednesday morning following Tuesday's smash.

The Keilor East scene was made safe for Victoria Police to access shortly before 5.30pm - almost 10 hours after the crash.

The smash involved a fully-loaded B-double tanker, which may have taken evasive action because of the driving of another vehicle, police say.

About seven cars and another truck were involved.

Police say a 49-year-old Ascot Vale man was killed when his car was flattened.

On Tuesday afternoon, officers could not confirm if anyone else was in the car until they were given access to the scene.

Five people were taken to hospital in a stable condition, most with neck, shoulder and facial injuries.

Three other people were assessed by paramedics at the scene but did not need to go to hospital.

Video shows a flattened car, another on its roof and a long line of cars that crashed behind.

The tanker was carrying 60,000 litres of diesel and unleaded petrol.

Up to 20,000 litres of unleaded petrol has leaked, most of it into nearby Steele Creek.

Firefighters covered the leak in fire-retardant foam and disconnected car batteries to prevent a fire.

The remaining fuel was decanted from the tanker so it could be righted and removed.

Absorbent booms have been put in the creek to contain pollution from the fuel spill and fire-retardant foam, with works underway to remove the contaminants.

"I don't think you get much worse than this," Victoria Police Inspector John Kearney told media at the scene.

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

Toll, which operates the crashed tanker, said their "priority right now is to offer every support to the people impacted".

CALDER FREEWAY CRASH:

Where: Calder Freeway, near Milleara Road

When: 8.05am Tuesday

What: One loaded fuel tanker, another truck and up to seven cars

Known deaths: 1

Hospitalisations: 5

Firefighters: 45

Ambulance units: 8