OSAKA — The Osaka Municipal Government ordered Snow Brand Milk Products Co. to halt operations at its Osaka factory, where processed low-fat milk has been found responsible for sickening nearly 7,000 people.

The decision followed the Osaka Prefectural Government’s announcement earlier in the day that its researchers have detected staphylococcus aureus bacteria in low-fat milk produced at the factory, confirming the source of a mass food-poisoning case in the Kansai area.

The municipal government said that operations at the factory in Miyakojima Ward will be suspended for unspecified period of time until its safety is ensured.

Prefectural officials are inspecting 30 cartons of milk taken from victims’ homes. Of the five tested so far, all have been found to contain enterotoxin A, a poison produced by the bacteria, Osaka prefectural officials said.

Meanwhile, police began on-the-spot inspections the same day at Snow Brand’s factory here to check allegations that the firm’s slipshod production process is responsible for the tainted product.

Speaking at a news conference Saturday, Snow Brand President Tetsuro Ishikawa said that staphylococcus aureus bacteria has been discovered in a valve on the production line at the suspended Osaka factory but did not know its cause.

“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 in Osaka.

As of 5:00 p.m. Sunday, a total of 6,921 people have fallen ill in Osaka, Kyoto, Hyogo, Wakayama, Nara and three other prefectures, with 41 remaining in hospitals.

The police inspection is centering on a valve that allows low-fat milk left over in the production process to flow into a spare tank, where the bacteria was found.

According to Snow Brand, the valve was supposed to be washed once a week but company records show it was last washed June 2.

Also, when the company staff disassembled the valve on Thursday to check for contamination, they discovered a mass of solidified milk the size of 10 yen coin inside it, company officials said.

With the firm admitting to the contamination, police decided early on to initiate an inspection, given the number of victims and the social impact the incident will have, police said.

They also decided an early inspection was necessary because the company might change the production line in preparation for resuming operations, they added.

Investigators were questioning the factory manager and those in charge of production.

to determine the link between the bacteria and people’s health, on suspicion that the Food Sanitation Law has been violated.

The dairy company came under light after thousands of people in western Japan complained about diarrhea, abdominal pains and vomiting after drinking Snow Brand low-fat milk on Tuesday and Wednesday. All were found to have drunk milk processed at the firm’s factory in Osaka’s Miyakojima Ward.

The bacteria was found during the firm’s inspection of the production line as its staff swabbed the inner parts of pipes and valves in 95 places to check for possible contamination.

Staphylococcus, or staph, is a common bacteria that can cause diarrhea and vomiting in people with weakened immune systems.