PORTLAND, Ore. – Six people, including at least three children, have been infected with E. coli at Montessori preschool of Alameda in Northeast Portland.

Four of the people, including two children, had the O157:H7 strain of E. coli, which health officials say is the most severe type of the bacteria.

Two of those cases genetically matched the strain found in the recalled I.M. Healthy SoyNut Butter that sickened 16 other people in nine states.

Two other children in Clackamas County were also infected by the soynut butter, according to state health officials.

The bacteria causes diarrhea and can produce a toxin that damages blood vessels, particularly in the kidneys.

"We are working closely with families, staff, and school administrators to stop the spread of this infection and understand how this outbreak happened," said Dr. Jennifer Vines, Multnomah County Deputy Health Officer.

More: Two Oregon E. coli cases linked to recalled peanut butter substitute

Most people with O157 strain of E. coli get better within five to seven days but others can have severe or life-threatening infections. Parents with questions about E. coli symptoms should consult their healthcare provider. More information about E. coli can be found here.

The Health Department is working with the school to prevent the spread of the illness.