South Korean prosecutors said Thursday they started looking into a complaint filed against McDonald’s Korea, whose undercooked patties allegedly sickened a 4-year-old.

The investigation came a day after the child’s parents filed the complaint against the Korean unit of the global fast-food giant for violating food safety rules, claiming that their daughter developed a hemolytic-uremic syndrome and had lost 90 percent of her kidney function after eating a burger from a McDonald’s outlet. 

On the same day, the Ministry of Food and Drug Safety notified 11 fast-food chains operating in South Korea, including McDonald’s, to cook patties properly to prevent food poisoning, its official said.

According to the parents, their daughter started expressing pain in her stomach a few hours after she consumed the burger in September 2016 at a McDonald’s in Pyeongtaek, Gyeonggi Province.

Her pain kept worsening until she was admitted to an intensive care in a hospital for two months.

The parents said their daughter now spends 8 to 10 hours a day at home receiving peritoneal dialysis due to permanent damage to her kidneys.

“McDonald’s failed to inform customers of risks (associated with undercooked patties), especially when HUS can severely affect children,” victim’s attorney told reporters Wednesday after filing the complaint to the prosecution’s office.

“It’s been found that some McDonald’s stores accidentally put the grill on a wrong setting and fail to cook patties fully,” the attorney claimed.

McDonald’s Korea expressed regret over the alleged food poisoning and said it would fully cooperate with the investigation.

By Bak Se-hwan (sh@heraldcorp.com)