Four RFS Riverina brigades and Fire and Rescue NSW Turvey Park were called to the incident at about 10am on Saturday when a train stopped south of Uranquinty.

Both the railway line and Olympic Highway were shut on Saturday as crews worked to contain the grass fires, which did not present a threat to property.

RFS Riverina duty officer Rex Sheather said it appeared that something on the Melbourne-bound train had caused the fires.

“It was definitely caused by the train,” he said.

“The driver was out and using a fire extinguisher underneath the train.”

Having brought the fire under control by Saturday afternoon, firefighters were called to the scene again at 4.30am on Sunday.

“We had a triple-zero call because somebody saw a burning tree,” he said.

The incident was again listed as under control by about 4.45am.

“We’re just mopping up (on Sunday),” Mr Sheather said.

“There aren’t any current warnings for drivers on the highway.”

Mr Sheather said it was a concern that some drivers passed the scene on the highway travelling at or close to 100 kilometres per hour.

In September, NSW brought in a new law requiring drivers to slow to 40km/h when passing police cars, fire trucks and ambulances displaying their red and blue flashing lights.

Mr Sheather said the law helped protect firefighters working beside the road.

“Slowing to 40km/h is the law now. It looks like we need to get a reminder out there,” he said.

Failing to slow down when passing emergency vehicles beside the road can result in a $448 fine and three demerit points.