Orange City Junior Rugby club president Tim West said a lot of club equipment had been destroyed in the fire at Pride Park in north Orange after the gear was being stored in the grandstand building.

"There was a brand new kit of jumpers, there were two boxes [about 30 in total] of brand new balls," he said.

Mr West said goalposts, collapsible shade covers, kit bags for the various teams, clothing and other items were lost in the blaze.

"All our football posts, padding and corner posts, we'll have to acquire them," he said.

Mr West said the fire, and the suspicious nature of how it had started, was "frustrating" for him and the club.

"I reckon it would have to be someone who's not part of a sporting organisation. You just don't do that," he said.

Mr West said the grandstand and facilities were also used by other groups.

"It is used for community purposes," he said.

Mr West said the club was at least fortunate the canteen and the bar area had survivied the blaze, receiving only smoke damage.

"The firefighters have done a terrific job saving them," he said.

"The canteen and the bar, they're the tools of our trade," he said.

"That's how we make our money."

Mr West said the club had about 120 junior players.

He said they would await an insurance company assessment before deciding how they would rebuild their stocks ahead of next year's season.

The Orange City senior rugby club also suffered the loss of equipment, gear and clothing in the blaze.

It will also be waiting for insurance company and engineering assessments of the building damage and the amount of loss.

Police are continuing their investigations into the fire which was reported about 2.15pm on Saturday.

Fire crews extinguished the blaze before handing the site over to police as a crime scene.

A police statement said the fire caused significant damage to the stadium's seating, roof and storage sheds.

"A crime scene was established and examined by forensic specialists," it said.

"The fire is being treated as suspicious and anyone with information is urged to come forward and contact Crime Stoppers on 1800 333 000."

Police have also asked any local residents with CCTV footage to contact them.