TOKYO (AP) _ Fumigators sprayed disinfectant Wednesday throughout the 92 elementary schools of Sakai, the Japanese city hardest hit by a deadly form of food poisoning apparently spread through school lunches.

Sakai, in western Japan, reported at least 5,262 people sickened by the E. coli 0157:H7 bacteria _ the same strain that three years ago caused at least 500 people who ate undercooked hamburgers to fall ill in Washington state.

Nationwide in Japan, the bacteria has killed four people _ three children and an 84-year-old woman _ and made 6,000 ill.

Health and Welfare Ministry official Yasuyuki Osada said there have been more E. coli infections among Japanese children in the past three weeks than there are food poisonings nationwide in an average year.

No one has died of the bacteria in Sakai, but city officials said they feared the situation was getting worse. ``We seem to be getting further from a solution,'' Sakai Mayor Hideo Hataya said.

Sakai parents brought about 500 children Wednesday to overflowing hospitals and clinics. Schools closed Saturday, a week early for summer vacation, making way for fumigators wearing backpacks of disinfectant to spray classrooms and bathrooms.

The bacteria is as easy to kill as other germs, said Osada, of the health ministry, but it is hard to control because it is so powerful. It takes about a billion salmonella bacteria to make someone sick, he said, compared to just a few dozen E. coli 0157:H7 bacteria. E. coli can live in a great many different types of foods.

So far, no companies have been singled out, although authorities are looking into the possibility that improper handling of food caused the outbreak in Sakai.

Sakai officials have closed many school swimming pools and set up a task force to handle the epidemic with plans to distribute pamphlets on hygiene. Members of the task force also inspected companies that deliver daily meals to the schools.

As fear of infection spreads, sales of kitchen bleaches and other household germ killers have more than doubled nationwide over the past two weeks, said Yukiko Hayakawa, a spokeswoman for Kao Corp., a maker of detergent, shampoo and cosmetics.

Many victims, including at least six infants, have developed a complication that attacks the kidneys as the bacteria attaches to the intestinal lining and secretes its poison. Most of the sickened have bloody diarrhea and flu-like symptoms. At least one young girl is unconscious, and more than a dozen are suffering serious kidney damage.