Operators of a kindergarten in Ansan, Gyeonggi Province, have been under fire due to outbreaks of enterohemorrhagic escherichia coli (EHEC) infections, leading to hemolytic urethral syndrome (HUS) in children.

HUS, also called hamburger disease since the mass outbreak in 1982 through undercooked hamburger patties in the U.S., is infected through EHEC. EHEC produces shiga toxin during human infection and causes damage to the colon's mucous membrane, showing symptoms of bloody stool and abdominal pain.

The recent mass food poisoning of children is raising concerns about the hamburger disease in Korea. (Getty Images)

According to the Korea Centers for Disease Control and Prevention, 114 kindergarteners and their families were under epidemiological investigation, and 58 patients were confirmed of EHEC infection. Among the confirmed cases, 16 have shown HUS, and four are receiving dialysis.

Ansan municipal government said six food items that the kindergarten used for lunch had been inappropriately stored and may be responsible for the mass food poisoning. Still, the exact circumstances have yet to be known.

The KCDC said it would conduct additional epidemiological investigations, such as analyzing children's food intake and tracking food ingredients with local governments. It would continue monitoring for other cases and suspected HUS patients and conduct genetic tests on confirmed samples.

"The confirmed patients are mostly children, the director of the kindergarten, an employee, and a family member of two to three years old, were also infected," KCDC Director Jung Eun-kyeong said. "We are checking the path of infection, such as playing with water, as EHEC can be infected by water, food, or hand."

Meanwhile, the local police are likely to start an investigation as seven parents of children have filed a complaint against the head of the kindergarten on charges of violating the Food Sanitation Act and professional negligence resulting in injury.