THE Department of Health has backed a manufacturer's claim that infant formula contaminated with pieces of aluminium does not pose a serious threat to children. Batches of Frisolac H and Frisomel milk powder were recalled on Monday after two mothers complained of metal pieces in the formula four weeks ago. A spokesman for the Department of Health said: ''We have taken the view that there are no long-term health risks involved with the contamination, although we are carrying out tests on the affected powder at the moment.'' The department was alerted when the local agent for Dutch manufacturer Friesland, Edward Keller Ltd, started to withdraw the milk powder from the market. More than 60 per cent of the 54,000 affected tins which went on sale in Hong Kong are back in warehouses, with no reports of babies becoming ill or swallowing pieces of the metal. Edward Keller said the recall of the affected batches would continue until the company could be sure virtually none was left in the marketplace. Renato Dell'Orto, general manager of Edward Keller's healthcare division, said: ''We have had about 500 calls from concerned parents but there have been no reports of illness or indications that any babies have swallowed aluminium pieces. ''My two-year-old son is on Frisomel so I understand the concern parents are feeling.''