New South Wales police are investigating claims a woman found a needle inside an apple she bought from a Woolworths in Sydney's north-west.

The sharp object was reportedly discovered inside a Pink Lady apple, which was purchased in a packet of six from a supermarket at The Ponds.

The Kellyville Ridge woman said she came across the needle while peeling a piece of fruit for her daughter's school lunch early this morning.

Needles found in punnets of strawberries have recently sparked a massive recall of brands, including Berrylicious, Donnybrook and Berry Obsession.

The strawberries were sourced from Queensland farms, many of which have been forced to destroy crops because of contamination fears.

Detective Superintendent Danny Doherty said other incidents of food contamination are now being reported across the state.

"We are investigating more than 20 incidents in New South Wales, but nationally, the number is much higher," he said.

NSW Police dismissed the apple case as an isolated incident, as well as a needle found in a banana in Bankstown on Monday.

"We are starting to get reports of other fruit contamination, so we would ask the public to chop up your fruit, particularly for kids," Superintendent Doherty said.

"It's not funny — we are at a point where we are having little kids nearly bite into a strawberry or other pieces of fruit, who could suffer serious injuries."

Queensland authorities first revealed cases of needles being found in strawberries last week, but the contamination scare has since spread to other states. ( Facebook: Joshua Gane )

No arrests have been made and the motive remains unclear, but NSW Police said anyone engaging in copycat behaviour would be punished.

"My message to them is you are making going to the supermarket a perilous task — and we will track you down, and you will face serious consequences," Superintendent Doherty said.

Some growers are now installing metal detectors to reassure consumers that their produce is safe, while others have reported huge losses.

Anyone caught contaminating food could spend up to 10 years behind bars.