Retired school teacher Patrick McMullen said he cut up a block of tasty cheese on Wednesday but, when he popped the cheese into his mouth, he bit into something hard.

"It felt like my tooth had broken. I spat it out and it was a safety pin. I could easily have swallowed it, but I didn't," the Orange resident said.

Mr McMullen said he immediately contacted Woolworths to alert them about the safety pin.

"I was really concerned about whether this was an isolated incident, possible sabotage, or a breakdown in the quality of manufacture. I was really concerned that this stuff was still on shelves all around the country," Mr McMullen said.

"Safety is my 100 per cent motivation. I told Woolworths that the last thing I wanted was to hear on the news that someone had choked on a foreign object in a block of cheese. As unlikely as that may be, I felt it was my moral duty to have Woolworths withdraw these from the shelves until they can guarantee the absolute integrity of the product."

A Woolworths spokesman said the company took such safety issues very seriously.

"Yesterday we were approached by a customer who has said he found a foreign object in a block of cheese," the spokesman said.

"We immediately withdrew the product from sale and instigated an investigation into the incident including with our supplier. The investigation is ongoing and we continue to speak with the customer."

Mr McMullen said Woolworths collected the cheese and safety pin from his home on Thursday afternoon and sent them to Melbourne, where they were being tested.

"I've been shopping at Woolworths all my life and I'm nearly 60. If there's not a satisfactory outcome, it will affect where I shop," Mr McMullen said.