Investigators believe a B-Double truck travelling west on the Western Highway and a semi trailer travelling east collided head-on about 11.30pm.

A third semi-trailer driver was unable to stop his vehicle in time and collided into the rear of the semi travelling east, leaving the male driver with life-threatening injuries.

All vehicles went up in flames.

Police spokeswoman Belinda Batty said the fire prompted a major fire-fighting effort that lasted several hours.

Police have located two bodies at the scene, which are yet to be identified.

The Western Highway will remain closed until at least midday as the investigation continues.

District 16 Country Fire Authority operations manager Chris Eagle said fire-fighters had been there since about 11.30pm.

He said 20 vehicles attended during the night.

Units from Stawell, Great Western, Ballarat, Wendouree and Ararat were still at the scene, sifting through hot spots in the wreckage.

Mr Eagle said breathing apparatus crews were coming from Willaura, Beaufort and Horsham to help.

"We are hopeful that within the next couple of hours, we can hand over to Victoria Police for their investigations," he said.

Police will prepare a report for the coroner.