Public health authorities are trying to put two and two together as they attempt to work out how a small calculator ended up contaminating a batch of hot cross buns at an Adelaide supermarket.

Key points: Hot cross buns produced or packed on April 7 were recalled from the Pasadena Foodland

Hot cross buns produced or packed on April 7 were recalled from the Pasadena Foodland Plastic contamination was caused by a small calculator

Plastic contamination was caused by a small calculator SA Health is concerned a button battery could have entered the food chain

On Monday, the Pasadena Foodland in Adelaide's inner south issued a recall of buns packed on Sunday after pieces of plastic were found inside them.

It has since been determined the pieces were from a small calculator, but SA Health has issued an urgent warning to consumers that the calculator's button battery poses a potential hazard.

"The button battery, as far as I'm aware, hasn't been found," Dr Lease said.

"The concern with a calculator is that it contains a button battery, which, if swallowed, can cause serious injury or even death.

"It can cause burns to the oesophagus.

"It's children that we're significantly concerned about, particularly because small button batteries are hard to find."

While there have been no reports of injury so far, Dr Lease said anyone with concerns about themselves or their children should seek urgent medical advice.

The supermarket's general manager, Paul Mabarrack, said "about eight" customers have so far reported finding pieces of the calculator.

"We're on tenterhooks until we can find [the battery] or until we can be sure that this thing hasn't resulted in any harm to anybody," he said.

About 200 packets potentially affected

It remains unclear how the calculator ended up as part of the Easter baking process.

"The exact circumstances surrounding how a calculator ended up in a batch of hot cross bun dough is still being investigated, but there is no evidence of a deliberate act," SA Health said.

All hot cross buns baked on Sunday have been recalled. ( Food Standards Australia New Zealand )

Mr Mabarrack said about 200 potentially contaminated bun packets had been sold on Sunday and Monday morning.

He said the buns were baked onsite, and a more thorough investigation would be conducted on Wednesday.

"The fragments of plastic have little numbers on them, so we put one and two together and came up with a calculator," he said.

"The bakers do use calculators in their daily work to work out quantities of flour and water and those sorts of things, so it's a common tool in the bakery area."

SA Health said the recall applied to the following products, which were produced on April 7:

Choc chip hot cross buns six pack

Choc chip hot cross buns six pack Cranberry and white choc hot cross buns six pack

Cranberry and white choc hot cross buns six pack Hot cross buns six pack

Hot cross buns six pack Hot cross buns large loose

Hot cross buns large loose Hot cross buns fruitless six pack

Hot cross buns fruitless six pack Mini hot cross buns 12 pack

Mini hot cross buns 12 pack Mini choc chip hot cross buns 12 pack

Mini choc chip hot cross buns 12 pack Premium hot cross buns 500g

Premium hot cross buns 500g Various weights, six or 12 in a pack (packed on April 7)

The plastic fragments were initially discovered by a customer who made a complaint to South Australian company the Chapley Group, which operates the supermarket.

"The Chapley Group is proactively working with SA Health and Food Standards Australia-New Zealand to notify customers who may have purchased the affected products," Dr Lease said.

"We urge anyone who may have purchased the affected hot cross buns check the 'packed on' date, not to consume them, and return them to Pasadena Foodland for a full refund."

Mr Mabarrack said the bakers were "very upset" and "shell-shocked", and that affected customers were being offered other products in exchange.

"Some people have lost their appetite for hot cross buns temporarily," he said.

Concerned consumers have been advised to contact the Chapley Group on (08) 8374 5000.