China says as many as 6,244 children have been ill after drinking contaminated powdered milk.
1,327 are currently in hospital, of whom 158 are suffering or recovering from acute kidney failure. Three have died.
China's health ministry says the milk contained a toxic industrial chemical used to make plastics.
22 brands of powder were found to contain the chemical melamine, which was apparently added to make the milk appear higher in protein.
Four city officials and a company boss have been sacked in the health scare which has seen thousands of parents in southern China flood into Hong Kong to buy foreign-made milk powder.
Six people have been arrested.
They include two villagers charged with selling melamine and adding it to milk sold to the Sanlu Group, an owner of a private food additive shop who sold the chemical to milk dealers and two milk sellers who admitted to selling the tainted product.
