Firefighters were called to two small grass fires, that ignited within an hour of each other, near the central business district on Wednesday afternoon.

Police and firefighters received the first call out at 4.40pm to a vegetation fire burning off John Glenn Place.

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The second triple-0 call was received at 5.50pm to a small fire in grass near the Erskine Street bridge.

Fire and Rescue NSW Station Officer Chris Cusack said both fires are now under investigation by police.

"There's no clear clause and no reason why these fires should have started," he said.

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These two fires follow three separate suspiciously lit fires that started in the same vicinity overnight on Tuesday that are also under police investigation.

Station Officer said these fires were quickly extinguished thanks to Dubbo Regional Council maintaining the grass at a low level.

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Due to the ongoing drought conditions, the community has been asked to dispose of cigarette butts correctly and not to use any tools or equipment that could cause a spark and subsequently start a fire.

If you have any information on these fires call Crime Stoppers on 1800 333 000.

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