Two Sydney truck drivers killed in 'horrific' head-on collision

Police have described the scene following a fatal head-on collision between two trucks in Sydney's west this afternoon as "horrific".

The two drivers were killed on impact in the crash on Lenore Drive in Erskine Park, with both vehicles erupting into flames.

"It's horrific, it was chaotic. There's debris everywhere, there's obviously a lot of panicked people. It was horrific for the police who attended, all emergency services who attended," Insp. Simon Maund said.

Police believe a white semi-trailer crossed the road, crashing head-on into a fully-loaded Austral bricks truck.

Bricks were strewn across the road, crushing one of the cabins.

Police estimated the combined closing speed of the collision at 160km/h. 

"These blokes, they go to work to provide for their families and then they don't make it home in the afternoon. It's terrible," witness Justin Bonino told 9NEWS.

Investigators are still trying to piece together why one of the trucks crossed onto the wrong side of the road.

Traffic diversions remain in place tonight as emergency crews work to clear the crash site. 

For further traffic information, visit www.livetraffic.com.