The prosecution on Tuesday raided the local unit of McDonald's over allegations that undercooked burgers sold at its restaurants caused illness among some customers, officials said.

Prosecutors and investigators from the Seoul Central District Prosecutors Office seized documents, including those on food material management, from the office of McDonald's Korea in Seoul's Jongno Ward during the raid, officials said.

The raid came one year and nine months after nine groups of activists lodged a complaint with the prosecution against McDonald's Korea, the patty supplier and government officials over several charges including violation of the food safety law and injury stemming from negligence.

The so-called burger patty scandal dates back to July 2017, when the mother of a 5-year-old girl filed a complaint accusing McDonald's Korea of being responsible for her child's incurable kidney disease.

The mother claimed that her daughter was diagnosed with hemolytic uremic syndrome after eating one of its burgers served with an undercooked patty in July 2016. After a series of similar complaints followed, the prosecution launched an investigation into the allegations.

But in February 2018, state prosecutors decided not to file charges against the fast food chain, citing insufficient evidence to back the accusations. The prosecution only indicted three officials from a McDonald's burger patty supplier for violating hygiene control and food safety regulations.

The prosecution began a reinvestigation into the case in January last year after a new complaint was filed by the nine civic groups. (Yonhap)