BEIJING - Sanlu Group, a leading Chinese dairy producer, said it had found in its self-check that some of its baby milk powder products were contaminated by tripolycyanamide.

Babies suffering from kidney stones receive medical treatment at the No.1 Hospital of the People's Liberation Army (PLA) in Lanzhou, Northwest China's Guansu Province, September 11, 2008. [Xinhua]

It has decided to recall all the baby milk powder it had produced before August 6 this year.

Recently, quite a number of infant kidney stone cases were reported in Gansu and other provinces. Investigations showed that most of the baby patients had drank the Sanlu formula before.

At least one baby in the northwest province had died as a result of kidney stones.