Cadbury is investigating a report of nails in two of its chocolate bars after a NSW mother posted a picture to social media showing the nasty surprise buried inside the sweet treat.

Aimee Sutton attached the picture to Facebook on Tuesday night showing the bent metal nail apparently discovered inside the Twirl chocolate bar purchased by her son.

"Harry got two Twirl chocolates tonight from Coles Express in West Dubbo," she wrote.

"He opened one up in the car, there was a nail in it. We opened the other when we got home and broke it up and there was another one."

Ms Sutton told news.com.au her son didn't bite into the nail and wasn't injured. She has reported the incident to both Coles and Cadbury owner Mondelez International.

A Mondelez International spokeswoman said the company had been in contact with Ms Sutton and had arranged to collect the sample "so that we can conduct a full and thorough investigation".

"The quality and safety of our products is our number one priority, and we maintain stringent control of our manufacturing processes to ensure our products meet the expectations of our consumers, including the use of physical barriers, sieves and metal detectors," she said.

Coles has been approached for comment.

Last year, a series of needles found in strawberries caused a nationwide food scare and severely damaged the half-a-billion-dollar industry.

My Ut Trinh, a 50-year-old Queensland farm supervisor, was arrested and charged over one of the original incidents that sparked a series of copycats.

The woman, a former strawberry farm employee known as Judy, appeared in Brisbane Magistrates Court in November charged with seven counts of contamination of goods with intent to cause economic loss.

It was alleged she had grievances about her treatment at work, and police said the woman's DNA was found inside a contaminated punnet in Victoria as part of a two-month, complex investigation.

The crisis extended across the country, with all six states beginning investigations after reports of tampering where needles and pins were discovered in strawberries, as well as apples and bananas.

It resulted in tonnes of strawberries being dumped or going to waste around Australia, threatening the future of the half-a-billion-dollar industry.

In response, Coles and Aldi pulled all strawberries from their shelves, while Woolworths only removed the affected brands it stocked.