Metal needles were found in punnets of strawberries in all six Australian states, prompting a health warning.

A health warning remains in place to throw out or cut up strawberries across most of Australia after sewing needles were found in the fruit in all six states.

New Zealand has pulled the Australian strawberries from its supermarket shelves, as police investigate after metal needles were found in punnets of fruit across the country.

Nervous farmers fear a multimillion-dollar sabotage, with Queensland Strawberry Growers Association vice president Adrian Schultz blaming "commercial terrorism" for bringing the industry to its knees.

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"I'm angry for all the associated people, it's the farmers, the people who supply them, the packaging people, the truckies with families to support, who suddenly lose their jobs ... it's far-reaching," he said.

A farmer in Queensland says he will install a metal detector to check his produce while others are destroying their crops, rather than pick them, to save money, The Courier-Mail reports.

Professor Nigel Grigg, professor of quality systems at Massey University said it was hard to have effective control over a product within the supply chain, as chains were so complex. "Within factories and processing plants, well established process controls and sample-based inspection plans can detect normal processing variations, while metal detectors, visual, chemical and other checks act as a last line of defence before product leaves the loading bay.

"However, as product moves in a complex path from grower/processor to exporter to shipping company to retailer to customer, there is ample opportunity for individuals who are so inclined to deliberately adulterate the product.



"Wilful sabotage and illegal behaviour is almost impossible to guard against, since inventive individuals can potentially adulterate product with metal, glass, wood, biological or chemical hazards and contaminants - past examples having included dead animals and bodily fluids.



"As we have all experienced with air travel, the only safeguards would be airport-style security checks of all product carried out at ports of entry or by the final retailers. However, the costs of such security would be prohibitive, and it is hard to imagine what battery of tests could effectively identify all conceivable contaminants.



"Food 'terrorism' and illegal behaviour in national and international supply chains is not new and remains an ever-present threat. Consumer vigilance will always have to play a significant role."

Two contaminated punnets of Mal's Black Label strawberries have been found in separate towns outside Adelaide, with the latest in Morphett Vale.

The Mal's Black Label strawberries were grown in Western Australia, where a man on Monday reported to the York Police Station in regional WA that he'd found a needle in a punnet of strawberries.

The warning to throw out or cut up strawberries remains in Queensland, NSW, Victoria and South Australia.

Federal Health Minister Greg Hunt has ordered Food Standards Australia New Zealand to investigate whether there are supply chain weaknesses or systemic changes needed.

Coles supermarkets have pulled all strawberries from their shelves, except Western Australia, as a precaution.

Aldi supermarkets are returning non-contaminated strawberry brands to their shelves.

Berry Obsession, Berry Licious and Donnybrook Berries have recalled their strawberries nationwide.

Foodstuffs and Countdown, which are owned by Woolworths and control nearly the entire New Zealand grocery market, on Monday announced they had stopped sending out Australian strawberries to their stores.