OSAKA -- Bacteria has been discovered on the production line of a Snow Brand Milk Products Co. factory here that processed low-fat milk believed to have made nearly 5,000 people ill, the company's president said Saturday.

Tetsuro Ishikawa said company employees found staphylococcus aureus bacteria in a valve that carries low-fat milk left over in the production process to a spare tank.

"We do not know where the staphylococcus aureus originated from. Maybe the cleaning (of the production line) was insufficient. I would have to say it was an oversight on our part," Ishikawa told reporters at the company's West Japan branch office in Osaka.