The Bruxner Highway has reopened near Wollongbar tonight after a B-double cattle truck caught fire near Converys Lane.

One of two eastbound lanes remains closed, with traffic moving under a reduced 60km/h speed limit. Motorists are being urged to exercise caution and allow extra travel time. 

The incident began about midday and forced the highway to close in both directions for several hours.

The truck was carrying about 60 head of cattle when it caught fire.

Reports from the scene said cattle on the lower level were released and wandered into nearby paddocks and residential properties. 

Some animals on the upper level remained trapped inside longer, with some believed to have suffered burns, before all eventually made it out alive.

The driver, a man in his 50s, escaped uninjured.

Emergency services, Transport for NSW and a heavy vehicle tow truck attended the scene.

Crews also worked to clear diesel from the truck while local farmers helped move cattle to a safer area. 

Investigations into the cause of the fire are underway.

Thick black smoke and flames erupted from the truck, with the cause still being investigated (Photos: 7 News)