A woman who was a passenger in a truck involved in a fatal bus crash in Victoria's west has been charged by police with drug trafficking offences.

Key points: Two trailers detached from the truck and were hit by a bus, killing its driver

Two trailers detached from the truck and were hit by a bus, killing its driver The 36-year-old truck driver was interviewed by police last night

The 36-year-old truck driver was interviewed by police last night A 22-year-old passenger in the truck has been charged with possessing a drug of dependence

The crash occurred about 2:00am on Thursday when two trailers detached from a B-double truck and fell across the Western Highway near Horsham, blocking the road.

A bus behind the truck was carrying 45 passengers from Adelaide to Melbourne when it smashed into the underside of one of the trailers.

Bus driver Emil Pich, 60, was treated by paramedics but died at the scene from his injuries.

Two other passengers were flown to hospital with serious injuries and dozens of others were treated at the hospital in Horsham.

Ferntree Gully man Emil Pich was driving the bus when it crashed. ( Supplied: Bus Association of Victoria )

Police last night interviewed the 36-year-old Murray Bridge man who was driving the truck before they released him without charge.

A 22-year-old female passenger from the truck was also from Murray Bridge and has been charged with trafficking, possessing and using a drug of dependence, police said.

She has been taken into custody and is expected to appear at the Ararat Magistrates' Court today.

Bus driver's colleagues 'absolutely devastated'

Mr Pich was employed by the Firefly Express bus company, which said in a statement that he had worked there for 25 years and was a highly valued team member.

"The incident is having a considerable impact on all concerned, having lost both a team member and friend," the company's general manager Frank Bono said.

"We are all absolutely devastated by his passing.

"Our primary and most immediate focus is on Emil's family, those who are injured in the incident, and assisting the rest of our team with counselling and support."