A teenage girl has been airlifted to hospital after a packed school bus collided with a truck north-west of Melbourne.  

The crash took place on the Western Highway at Bacchus Marsh around 3am, as the bus the rolled down the 50 metre-deep embankment off the side of the main road.  

Heartbreaking photos show the students’ suitcases strewn across the hill as emergency services work to clear the highway.  

One girl suffered serious injuries, as did the male truck driver.

The other 26 students on the bus, along with four adults and the bus driver, have been taken to hospital for observation.

The group from Loreto College in Ballarat was travelling to Melbourne airport at the time of the crash, where they were set to travel to the Unites States to attend the  NASA space camp at the Kennedy Space Centre in Florida.

The Melbourne-bound lanes of the Western Highway are expected to remain closed for several hours, as motorists are being urged to take an alternative route  into the city.  

Parents are being asked not to attend the scene of the crash to find out information about their children, but rather to call Ballarat Police Station.

A spokeswoman for the school said the  principal would be holding meetings with worried parents, as they put a plan in place to deal with “the fall out from everything”.

She said, “Everyone is fine. We had injuries but there are no fatalities.”

Police are now investigating the cause of the crash.  

Image credits: 9News