The Centre for Food Safety has moved to allay local fears that Australian eggs on sale here may have been injected with toxic food dyes intended to make the yolks appear brighter. Strong dosages of chemical food dye additives are believed to raise higher risks of cancer and their sale is banned here.

The agency said Monday that it found no traces of substances banned in Hong Kong among 630 eggs samples examined over the past three years. But the center promised to continue monitoring the situation and to consult with the Australian government.

Louis Shih Tai-cho, physician and president of the Hong Kong Medical Association, told China Daily the issue is potentially serious and bears close scrutiny.

The agency's statement came in response to reports in Australian media, quoting several organic farmers as saying that artificial food dyes were being added to exported eggs from Australia.

Australia's leading egg producer Sunny Queen, a cooperative based in Queensland, signed an exclusive distributorship agreement with a local registered company in Hong Kong, Century Food Company, to sell its products at supermarkets in Hong Kong, Macao and the Chinese mainland.

Hong Kong's major supermarkets approached by China Daily said they do not sell Australian eggs, adding those are available only at high-end supermarkets.

Census and Statistics Bureau figures show Hong Kong imported a total of 2,117 million fresh eggs in 2013, the last year for which statistics are available. The great majority came from the Chinese mainland, the US, Singapore and Thailand.

The Australian news report however was critical of Australia's lax regulation on free range chickens.

Anyone convicted of selling food with unauthorized additives in Hong Kong is liable to a maximum fine of HK$50,000 dollars a day and six months' imprisonment.

Nick Li in Hong Kong contributed to the reporting.