Police investigating what caused blaze that tore through petrol station in Sydney's south-west

Authorities are investigating whether gas bottles are to blame for a large fire that took hold at a petrol station in Sydney's south-west.

Multiple fire trucks were called to a Metro petrol station on Hamilton Road in Fairfield about 12.45pm.

"Fire Rescue initially sent three trucks, 12 firefighters to this call, but crews en route observed large volumes of black smoke and requested more resources," Fire Rescue NSW Inspector Steve Brown said.

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"Thirteen trucks and over 50 firefighters are now either on scene or rushing to this emergency.

"Once on scene, firefighters were confronted with a fierce blaze and are now attacking the fire from several directions."

Witnesses said it was "a big fire".

"We couldn't see any smoke, just fire," one person told 9News.

NSW Fire and Rescue Superintendent Aaron Ross said there were people everywhere.

"There was a very intense large fire and with gas bottles involved as well, it was a very intense fire and quite a chaotic scene to start with," he said.

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Two residential unit blocks were evacuated as strong winds fanned the smoke in their direction.

"We were all panicked, we informed our neighbours and we got out. Cops made sure everyone evacuated the house," a resident said.

The fire was extinguished in the late afternoon, and residents were able to return to their homes.

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