At least five people were confirmed to have died in a mass outbreak of E. coli O-157 food poisoning in Hokkaido as of Monday, with 110 others likely suffering from O-157 contaminated Chinese cabbage pickles.

In addition to the five confirmed fatalities, two elderly women who were residents at a nursing home in Ebetsu, which is near Sapporo, have died after developing symptoms of food poisoning. However, O-157 bacteria has yet to be confirmed as the cause of their deaths. At least three other residents at the same facility have been hospitalized with serious symptoms.

It is strongly believed that the source of the O-157 outbreak was lightly pickled Chinese cabbage. The Sapporo-based food company that processed the cabbage is suspected of failing to properly sterilize the cabbage by heating.

Many details regarding how the E. coli O-157 infections reached epidemic proportions have yet to be clarified. One possible factor behind the mass food poisoning is a method of using less salt when pickling vegetables to suit consumer tastes.