Firefighters were initially called to a unit on Maxwell Street in Wellington at 12.15am following reports of a fire.

Fire and Rescue NSW (FRNSW) Wellington Captain Mark Moroney said upon arrival crews discovered that a fire had occurred in a cupboard of the unit and it had been extinguished by a neighbour.

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"The fire was out when we arrived," he said.

Firefighters checked the unit to determine that the fire was completely extinguished before leaving the scene at 1.15am.

Then at 2.30am, firefighters were again called to the same unit for another fire.

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"We were called to the same address in Maxwell Street and found the unit was well alight and completely involved in fire," Captain Moroney said.

"Upon our arrival the crews quickly contained the fire and prevented it from spreading to the other units."

Residents from the adjoining two units were immediately evacuated, with two of those residents treated on scene by paramedics for minor smoke inhalation.

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"The unit involved in the fire was completely destroyed," Captain Moroney said.

"I believe the unit was occupied, but the residents were out at the time."

At this stage the cause of the two fires are "undetermined", however, police were also called to the scene and the incidents are now under investigation.

FRNSW crews from Dubbo and NSW Rural Fire Service firefighters also provided assistance.

MAP: The location of Maxwell Street in Wellington