In May 2016, the FBI investigated reports of a man who had possibly contaminated food in a Michigan market.
The FBI has did not issue a general warning to Americans about possibly poisoned produce in grocery stores.
On 18 July 2016 the web site Q Political published an article whose alarming headline ("FBI Issues Horrifying Warning to Frequent Grocery Shoppers") and opening paragraphs suggested that federal investigators had issued a general warning to Americans about the United States' food supply:
The FBI issued a horrifying warning to frequent grocery shoppers, I can’t believe this! Every American needs to see this!
After one young man’s unthinkable actions, washing your fresh fruits and vegetables has never been more important.
Reports have now confirmed our worst fears, as cameras captured one young man visiting several grocery stores with the sole intent of spraying a poisonous mixture on open food throughout their produce sections.
The FBI has issued a warning about going to the grocery store, and advises consumers to dispose all foods recently purchased from salad bars.
Q Political linked to a Detroit Free Press article as a source for their claims, but the linked article (orignially published in May 2016) specified that concerns about affected grocery stores were limited to those in the area around Ann Arbor, Michigan, and that the FBI had investigated the alleged food contamination and linked it to a single individual there:
In a potential food poisoning scare, the FBI says it has arrested a man suspected of contaminating produce at open food bars at several Ann Arbor-area grocery stores with a liquid spray containing mice poison, hand cleaner and water.
State health officials say no one has yet reported getting sick from the potentially contaminated food, and it is not yet known if there is any threat to the public. But they are recommending that consumers throw out any salad bar, hot bar and ready-to-eat items that were purchased at potentially affected stores in Ann Arbor, Saline, Midland and Birch Run.
The newspaper didn't say the FBI issued a general warning about grocery store produce in the affected area (or anywhere else), just that the Michigan Department of Agriculture and Rural Development [MDARD] had advised residents of the Ann Arbor region to discard foods that had been "purchased from salad bars, olive bars and ready-to-eat hot and cold food areas from these stores between mid-March and the end of April":
The investigation has prompted the the Michigan Department of Agriculture and Rural Development to issue a public advisory, urging consumers to throw away any potentially contaminated food. State health officials said based on what they know about the ingredients in the mixture at this time, they do not anticipate any adverse health effects on individuals who may have eaten the potentially contaminated products.
"Out of an abundance of caution and to protect public health and food safety, I encourage consumers to dispose of any foods purchased from salad bars, olive bars and ready-to-eat hot and cold food areas from these stores between mid-March and the end of April," said Jamie Clover Adams, MDARD director. "Although most of these types of foods may have already been eaten or disposed of, some may still be in refrigerators or freezers."
We contacted MDARD to determine whether the July 2016 article was accurate, or whether it represented a continuation of events that occurred in March and April of 2016. An MDARD representative told us that the agency had issued the original salad bar warning "in an abundance of caution," that no one (to their knowledge) had been sickened by the reported incidents, and that a suspect in the case had been arrested in early May 2016.
The MDARD representative double-checked with the FBI to ensure that no such general warning had been issued. The original cautionary statement referred only to food from open hot or cold food bars or the produce aisle in one particular store, and only to items purchased between late April and early May 2016; the FBI did not (and has not) urged shoppers to avoid grocery stores in general+. (That remained the case when the already misleading claim was republished by Q Political on 12 May 2017.)