Parents are flocking to Vietnamese hospitals to have their children's kidneys checked, worried they may have consumed toxic melamine from Chinese milk products, health experts said Friday.

"We are checking the kidneys of 40 to 50 out of the 100 infants we see each day," said Ngo Thanh Loan, a nurse in the ultrasound department of the National Pediatric Hospital in Hanoi. Loan said normally only 10 to 20 per cent of children would have their kidneys checked.

Children's Hospital No 1 in Ho Chi Minh City performed checkups on more than 6,000 infants last week, 1,000 more than usual, according to local media.

Vietnam's National Hygiene and Food Safety Department announced Thursday it had found 18 milk products containing melamine being sold in Vietnam. Most were imported from China, but others came from Malaysia, Indonesia and Thailand.

Vietnamese media in recent days have reported that parents are discouraging their children from drinking imported milk, turning instead to local fresh milk or soy milk.

Melamine, an industrial chemical used in the manufacture of plastic, can cause kidney stones and other complications, particularly in infants.

In recent weeks Chinese authorities have revealed that dairy farmers in China have illegally used the chemical on a massive scale to increase the nitrogen content in their milk, thus increasing its apparent protein content and allowing it to pass quality control tests at distribution centres.

The revelations have led a number of countries to ban the import of Chinese dairy products.