An outbreak of E. coli O111 in central Japan has killed two children and two adults and sickened at least 56 other people, according to news reports this week.

The infections have been linked to a Korean raw beef dish called yukhoe, similar to tartare, served at a chain of barbecue restaurants.

According to media reports, one boy, a preschooler, was hospitalized April 21 and died six days later in Fukui Prefecture, while the second boy, age 6, became ill on April 24 and died April 29 in Tonami, Toyama Prefecture.

Both boys were infected with the same strain of E. coli O111 and both had eaten at the Yakiniku-zakaya Ebisu chain of restaurants run by Foods Forus Co., which has temporarily closed all 20 of its outlets. Four of the chain’s restaurants appear to be directly linked to the outbreak, a Jiji Press article reported Tuesday.

On Wednesday, a woman died of E. coli O111 complications. She, too, had eaten yukhoe at the chain’s restaurant in Tonami. Reports on Thursday said a second woman had died.

Of the 56 other cases, at least 19 involved “critical symptoms,” according to the Asahi Shimbun story.

According to Asahi Shimbun reports, Yasuhiro Kanzaka, president of Foods Forus Co., acknowledged that for the past two years his company had not tested its raw meat for bacteria, as required by the health ministry.

In the U.S., E. coli O111 is not considered an adulterant and there are no government testing requirements for it.