A woman living in London found a high-tech tracking device in a chocolate bar sent to her by relatives in New Zealand.
The complaint was among about 200 received by the Ministry of Agriculture and Forestry about food safety breaches since January last year.
The woman found a small watch-like battery in a Whittaker's Roast Almond Gold chocolate slab, which was part of a gift from family.
Whittaker's food safety manager Claire McKay told the Herald on Sunday the complaint was lodged via email and the company immediately issued an apology.
It was requested the chocolate be sent back to Whittaker's Porirua factory for investigation.
An external electronic expert found the sophisticated tracking device had been placed in the bar after it had left the factory.
It was determined it wasn't planted in the slab during the manufacturing process, because it would have been found by quality control systems.
Paragon Investigations director Ron McQuilter says the small device would have been pricey.
"Something that small isn't normal," he says.
"I'm imagining it would be very high-tech, which means it will be expensive."
Mr McQuilter says the person who put the device in the chocolate bar would have had to carefully open the wrapper and glue it back again.
"You see this kind of thing on the movies but you try opening something and put it back together again, it's not easy."
Other foreign objects discovered in food included a condom in a KFC meal, worms and maggots on supermarket pork and a sticking plaster on a pizza, according to the information obtained by the Herald on Sunday.
