TOKYO (AP) _ Japan's biggest maker of dairy products will suspend production nationwide on Wednesday to inspect its factories after thousands of people were sickened by tainted milk.

Snow Brand Milk Products Co. will halt operations at its 21 factories across the nation, Executive Vice President Akihiko Sasajima said at a news conference Tuesday night. The suspension was expected to last for a week.

Snow Brand was forced to recall its milk products after more than 11,000 people fell ill in Japan's worst case of food poisoning in decades.

Bacteria accumulated in a production-line valve caused the outbreak, which started when residents began suffering diarrhea and vomiting after drinking lowfat milk.

The staphylococcus aureus bacteria, or staph, can sicken people with a weakened immune system but is usually not lethal.

Snow Brand Milk President Tetsuro Ishikawa apologized to consumers and said he would resign on Sept. 30.

Police have begun investigating the possibility of criminal negligence.