Six trucks exploded into flames after a fiery crash that shut down a major NSW highway early on Tuesday morning.

Two trucks appear to have initially collided and careered into several other rigs at a roadside stop on the Hume Highway near Gunning, on the Southern Tablelands.

Six trucks were destroyed in the incident which happened around 5am. 

One truck was carrying eight tonnes of butane cans, resulting in multiple small explosions when fire crews arrived at the scene.

Also fuelling the resulting fire were loads of alcohol, resin, and memory foam being transported in the other trucks.

Emergency services had initially feared a seventh truck was involved, and its driver was missing. But police said at midday Tuesday that all people were accounted for.

“Emergency services were confronted with fairly horrific scene this morning and due to the smoke and the flames, we weren’t able to get close enough. However, we’ve just confirmed six trucks and six drivers with us as well,” a NSW Police spokesman said.

“Nothing short of a miracle there.”

NSW Ambulance responded to the crash and treated six male drivers for minor injuries. Police said two were taken to Goulburn Hospital for mandatory testing.

Fire and Rescue NSW has sent seven fire trucks, including two hazardous materials vehicles and up to 40 firefighters, to the scene.

The Hume Highway remained closed in both directions as of 11am.

Police said it may take some time to reopen the road given the extent of debris and potentially hazardous materials left in the wake of the crash.

A crime scene had been established and the Crash Investigation Unit will assist with investigations.

-with AAP