Updated 4:35 p.m. with new information
In a written statement, the state health department said that only 17 of the 26 people sickened reported having eaten anything from a Schnucks salad bar. The other nine did not.
Of the 26 E. coli cases confirmed by the Missouri State Public Health laboratory, 20 are from St. Louis County. The lab is still testing samples from other suspected cases.
The state says that so far, no food samples collected from any location have tested positive for E. coli bacteria or shiga toxin, its harmful byproduct.
The US Food and Drug Administration has now joined the Missouri Department of Health and Senior Services and the federal Centers for Disease Control and Prevention in investigating the source of the contamination.
The state health department says that investigation could now include distributors and producers located outside Missouri.