THREE weary fire fighters were minutes from home after volunteering at St George when they received yet another emergency call-out.

Mal Stacey, Peter Bolitho and Colin Payne were returning to Warwick after four days of cleaning out flooded homes, when they were then rushed to the scene of a hay truck on fire.

"We heard the call over the radio and came here to help back-up," Mr Payne said.

"We thought we'd volunteer our water supply. It's been a hectic couple of weeks."

The truck was travelling south towards Stanthorpe along the New England Highway and was about 10km out of Warwick when the drivers - two males - noticed the blaze.

They quickly pulled off the road and called for help. Both were uninjured.

A police spokesman said investigations were looking into two possible reasons for the cause of the blaze.

"Possibly the hay was near the exhaust or too close," the officer said.

"That or it could be internal combustion due to the hay possibly being wet.

"Scenes of crime were out at the site having a look and we're investigating those couple of avenues."

About 400 bales of hay were lost in the blaze.

Police couldn't specify any more on the male drivers, including where they were coming from and driving to. It is also unknown where the hay was from.

A 300m stretch of New England Highway was closed to traffic as thick smoke hovered over the road while emergency crews brought the blaze under control.

The road was closed momentarily, after which Main Roads used stop-go traffic direction for one lane.

Rural Fire Brigade personnel were still on the scene at 4.30pm using water at a nearby dam to keep the hay damp.