The Milwaukee Health Department is searching for the source of E. coli bacteria that has sickened at least 11 Milwaukee County residents.

Those infected by the bacteria E. coli O157:H7 include eight children. Five required hospitalization at Children’s Hospital of Wisconsin. Of the five, two were treated and released while three remain hospitalized, said hospital spokeswoman Erica Halbleib.

Health officials say the cases don’t rise to the level of an outbreak and that no additional cases have been reported to them since Monday.

The bacteria can be found in meat, sprouts, watermelon, lettuce, unpasteurized milk and juice, as well as contaminated water. It can also be contracted by petting farm animals.