Explosions could be felt kilometres away, with a massive fireball reaching heights of 150 metres.
About 200 firefighters tackled a massive factory fire in Sydney's west, with authorities warning it could burn for days.
Emergency services were called to a waste management business in Kurrajong Street, North St Marys at about 10.50pm last night.
Explosions were heard as the blaze began, with some being felt several kilometres away in Penrith.
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A fireball was seen high above the site, reaching 150 metres into the air.
Concrete blocks were sent flying 150 metres into the air and locals were told to keep windows and doors closed.
The fire could still burn for several days, as hazardous materials at the business, a recycling centre, is feeding the inferno.
Two firefighters were treated at the scene for minor burns, with fire crews being praised for their valiant efforts to contain the raging fire.
"There's been some amazing firefighting going on," Fire Commissioner Jeremy Fewtrell said.
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"We've had an incredibly large explosion, and so luckily all of our firefighters were able to be safe through that."
Large chunks of rock were thrown into the air in the initial explosion, hindering initial efforts to combat the massive blaze.
Explosions had continued throughout the morning, with locals warned to avoid the area and to keep their windows closed, as smoke continues to billow from the fire.
Drones with air monitoring devices were deployed giving fire crews eyes in the sky mapping out where the toxic fumes had spread.
Whilst the cause of the fire remains unknown at this stage, police are conducting their own investigations.
A 200 metre exclusion zone has been put in place, with motorists urged to avoid the area.
Firefighting has now been scaled back as investigations begin.
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