A man who went into multiple Michigan grocery stores and sprayed a poisonous mixture on open food is in custody, according to the FBI.
About 15 stores -- including a Whole Foods Market and a Kroger -- in Ann Arbor, Flint, Midland, Birch Run and Saline may have been targeted, according to the Washtenaw County Public Health Department.
"It's just absolutely crazy. Why would somebody do that?" a customer outside Whole Foods Market told CNN affiliate WDIV.
Though the department says it has not received any "unusual reports of illness," it says it's received reports of vomiting and diarrhea that "are being actively investigated for possible connection to this incident."
The suspect admitted to spraying a "potentially hazardous material" -- a liquid combination of water, hand cleaner and mice poison -- on produce in three stores within the past two weeks, the FBI said.
Investigators are trying to determine whether any other stores were affected.
County officials advised consumers to throw away any food from salad bars, olive bars and ready-to-eat hot and cold food areas purchased from affected stores between the middle of March through the end of April.
"While the risk for adverse health effects appears to be low, more investigation is being done to determine what level of exposure may have occurred," said Dr. Eden Wells of the Washtenaw County Public Health Department.
A list of the potentially contaminated stores can be found at the county public health department's website.