UPDATE, 8AM: The accident scene has now been cleared and traffic is starting to flow more freely through the area.
EARLIER: A man has been airlifted to hospital with head injuries following a multi-vehicle crash on the Western Freeway this morning.
Two trucks and two cars collided near Pentland Hills about 4.20am, leaving at least two people in hospital.
One car flipped and the driver aged in his 50s was trapped in the vehicle for about an hour.
He was treated by paramedics while SES rescue teams worked to free him from the vehicle.
He was airlifted to The Alfred hospital in a stable condition, with head injuries and grazes.
A second man has been taken to the Royal Melbourne Hospital, although injuries are not yet known.
Two lanes are closed and only one lane is open Melbourne-bound, although at least one lane is expected to be open soon.
Emergency services on site and delays are expected.
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