Things are getting worse for Chipotle Mexican Grill Inc. Last month, the Denver-based fast- food company announced that the U.S. Food and Drug Administration's Office of Criminal Investigations is looking into a suspected norovirus outbreak that sickened more than 130 people who ate at a Sterling, Virginia, restaurant in June.

Last year, the U.S. Department of Justice launched an investigation after salmonella, norovirus and E. coli traced back to Chipotle's Tex-Mex-themed chain restaurants wreaked havoc in 2015 from coast to coast, sickening more than 500 people. Those incidents included a norovirus outbreak in Simi Valley, California, that sickened 234 people and another in which 140 Boston College students got ill.

Also this summer, two senior executives at an egg company in Iowa that was central to a nationwide salmonella outbreak in 2010 exhausted their appeals. A federal judge ordered Austin “Jack” DeCoster and his son, Peter DeCoster, to begin serving their three-month prison sentences. The pair pleaded guilty in June 2014 to the misdemeanor charge of introducing adulterated food into interstate commerce.