The north-bound Honda lost control on the Hume Highway and spun into the path of a truck heading the opposite way about 10.50am on Sunday. The men, all aged in their 20s, died at the scene.

NSW Police Commissioner Andrew Scipione said yesterday, ''We're still working through some things that we found in the vehicle.

''There may be some allegation that we may have found some powder and a quantity of cash.

''Now, we don't know if that, in any way, adds to or is responsible for what we've got out of this horrific scene, which is four fatalities and a truck driver that's traumatised forever.'' Mr Scipione did not comment on whether the power was cocaine.

Fatigue was suggested as a contributing factor to the crash, but Mr Scipione said alcohol might also have been involved.

Truck driver Leo Kearney, aged in his 50s, was taken to hospital with leg and head injuries.

''You're looking at 60 tonne, a lot of these trucks, and unfortunately as things happen you can't just stop them on a dime,'' he said.

Mr Kearney swerved off the freeway to try avoid the collision. His rig ended up in roadside bush.

Mr Scipione said emergency crews were faced with ''absolute carnage'' when they arrived at the scene of the smash. The men were four of seven people killed on NSW roads at the weekend, taking the state's road toll to 412. AAP