About 1,000 babies aged one to eight months need to have their blood tested after being fed two Japanese-made infant formula that were banned in Hong Kong yesterday.
The seriously low level of iodine in the milk has sparked a thyroid scare, with slow mental growth a danger.
The ban follows tests by the Centre for Food Safety on 40 products from 14 milk brands.
The tests began last year but, because of the low iodine level found in two Japanese brands, Secretary for Food and Health Ko Wing-man yesterday urged parents to take their babies to maternal and child-health clinics for checks from tomorrow.
Low intake of iodine in milk may slow the production of thyroxine hormone in the thyroid gland, leading to possible mental and physical retardation.
Wakodo Infant Formula and Morinaga Infant Milk Powder were banned and pulled off the shelves for containing just one-third of the World Health Organization's recommended levels of iodine.
Four other brands were also below WHO guidelines but met the exporting countries' standards for iodine.
A government spokesman said these are Meiji Infant Formula made by Japanese company Meiji Corporation; Snow Brand Smart Baby made in Australia, although its parent company is from Japan; Physiolac Infant Milk 1, made by France's Laboratoires Gilbert; and Friso Infant Formula Milk 1 made by Friesland Foods of the Netherlands.
Ko, speaking at a press briefing, denied there was a delay in telling the public.
Two samples of each of the 14 powdered milks were taken and the results were available by the end of last month. Six products had iodine lower than WHO levels but repeat tests had to be carried out.
Risk assessment and tests results came in on Monday, he said, and yesterday the Department of Health arranged blood tests for the babies from tomorrow.
Ko said he advised mothers who use the banned milk to breastfeed their babies or switch to other brands with acceptable iodine content.
He insisted the ban and checks are precautionary. There have been no cases of infants suffering physical retardation or brain damage from the banned milk.
Centre for Food Safety consultant Philip Ho Yuk-yin said both banned brands made up less than 3 percent of the formula market in Hong Kong.
Center controller Gloria Tam Lai- fung said Japanese mothers have naturally high levels of iodine, which may have led to lower levels in milk powder.
Tam said she expects to finish testing the rest of the milk formula in the first half of next year.
A spokeswoman for Wakodo Corporation's Hong Kong agency said it was informed yesterday.
A spokesman of Morinaga Corporation's Hong Kong agency said it is following up the issue.