People who drank unpasteurized, or raw, milk from the Dee Creek Farm were asked to contact their health department, whether they were sick or not.
The dairy was shut down, and authorities planned to inspect its milk and bottling operations.
Infection with E. coli bacteria has been confirmed in eight children, ages five to 14. Four of them were in serious condition at hospitals, officials said. Three unconfirmed cases have been reported in Oregon.