That was in January, well before news surfaced that another Yili product was tainted with the potentially harmful chemical melamine.

On Thursday, Xinyang's worried parents brought him the National University Hospital children's clinic. The unit has started a special service for kids who may have been affected by melamine contamination.

As a doctor pressed gently on Xinyang's abdomen to check for kidney stones, a byproduct of melamine ingestion, his parents, Mr Chen Jin and Madam Yang Xin, looked on anxiously.

But after the check-up, a urine test and an ultrasound scan he was declared healthy.

Six children have been examined since the service began on Tuesday, including Xinyang. None were found to have melamine-related kidney problems.

His family, originally from Tianjin, was visiting relatives in China last December when they began drinking Yili milk.

When they came back, they continued to buy it because Xinyang liked its 'richer flavour,' said Mr Chen, a 39-year-old engineer who is a Singaporean citizen.

They have since switched to a brand made from Thai milk.

'We don't dare to drink milk from China any more,' said Madam Yang, 40, an electronics laboratory executive.

Earlier this week, the Ministry of Health told hospitals and family doctors to be on the lookout for possible cases of melamine contamination in children.

Suspected cases should be referred to specialists for treatment, the ministry said.