Hundreds of parents swamped a Hong Kong hospital Monday to have their children checked after a 3-year-old girl became ill with a kidney stone from contaminated Chinese milk.

The Princess Margaret Hospital, designated to deal with all contaminated milk cases in the city of 6.9 million, struggled to cope as huge crowds overran its emergency unit.

Parents faced waits of hours just to see doctors for checks on their children, many of whom were crying and complaining of pains and stomach cramps.

The first victim was treated and released from hospital Saturday but the case triggered alarm among parents across the city who have been feeding their children with milk imported from China.

Tests on milk in Hong Kong found several samples infected with melamine, the industrial chemical that has killed four babies and made thousands more sick in China.

Among the samples found to contain the chemical include milk made by food giant Nestle in China, which has now been removed from supermarket shelves across the city.

More than 50 per cent of milk products in Hong Kong are imported from mainland China. Milk supplies to the city were curtailed Monday as new quality checks were introduced in the wake of the scandal.