A 2.5m adult boa constrictor is "on the loose" in NSW after freshly shed snake skin was found at a property west of Sydney.

The NSW Government issued a warning to the public on Friday, after the snake's skin was found two days earlier at a building site on Torumba Circuit in the Cascades Estate in Silverdale.

Authorities warned people not to try to capture the snake. Photo / Australian Snake Catchers
Authorities warned people not to try to capture the snake. Photo / Australian Snake Catchers

Biosecurity officers are scouring the Cascade Estate for the huge reptile, amid fears small pets and even children could be at risk.

Locals have been asked to be on the lookout for it and to report any sightings.

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The Australian Snake Catchers posted images of the skin to its Facebook page warning people to call professional reptile handlers if they spot the snake.

"Any sightings of the snake should be swiftly reported," they posted on their page. "We have been out to the property and conducted an extensive search of the surrounding area. DO NOT ATTEMPT TO CAPTURE THIS SNAKE."

Scott Charlton from NSW Government also warned residents to not make contact with the animal if they see it.

"Observe and, if possible, photograph the animal," he wrote in the letter to residents of The Cascades Estate. "If it is moving try and watch where it goes."

The snake shed its skin at a construction site in a small NSW town. Photo / Australian Snake Catchers
The snake shed its skin at a construction site in a small NSW town. Photo / Australian Snake Catchers