A rubbish recycling factory in North St Marys was destroyed by fire early this morning.
While there was no one inside the factory at the time of the fire, a Fire and Rescue NSW spokeswoman said there were concerns a number of structures inside the complex could collapse.
Gas cylinders inside the factory also triggered a number of small explosions during the fire.
Fire and Rescue NSW crews were called to the factory on Plasser Crescent, just off Kurrajong Road, at 2.09am after receiving multiple triple-0 calls.
Ten fire crews responded to the blaze. They arrived at the scene to find the two-storey complex well alight.
Crews from Dunheved Fire Station were the first on the scene, as the fire station was over the road from the factory.
Firefighters managed to prevent the fire spreading to nearby homes and businesses, with no evacuations as a result of the blaze.The fire was brought under control just before 3am, with the blaze totally extinguished by 4.30am.
The Fire and Rescue NSW spokeswoman said crews were still on the scene helping to clear the damage.
In a Facebook post, Dunheved Fire Station praised the quick response of their crew.
"The fire was confined to the processing area of the facility and did not spread to the office, machinery workshop/store nor to the several adjoining properties," the post said.
At this stage, the cause of the fire is unknown, with an investigation underway.