An outbreak of E. coli O157:H7 has sickened at least nine people on the Hawaiian island of Oahu, reported state health officials this week.

Victims of the outbreak, which began in mid-February, include six children and three adults, according to the Civil Beat. Four of the victims – one adult and three children – have been hospitalized. The three children were treated for hemolytic uremic syndrome (HUS), a potentially fatal complication of E. coli infection that causes kidney failure.

One child remains in the hospital but is recovering. All but one of those sickened live on the island. The non-resident was visiting from Canada, reported the Hawaii Department of Health Disease Investigation Branch, which sent out a warning letter to Oahu healthcare providers last week.

Health officials say they have yet to pinpoint the source of the bacteria. The people who were infected belong to different families and live in different places around the island.

“We’ve been doing the investigation but as of right now, there has not been any identifiable commonality among the cases,” said Michele Nakata, chief of the DOH’s Disease Investigation Branch, reported Civil Beat. “They didn’t participate in the same kinds of activities. They didn’t eat the same types of food items. And they didn’t go to the same restaurants or anything like that. So it’s been fairly complicated.”

In the meantime, DOH recommends that consumers use safe food handling practices in order to avoid infection.