Authorities are in the midst of a massive recall after an outbreak of Listeria sickening 12 people was tied to a Dole facility in Ohio that produces bagged salads.

The Centers for Disease Control and Prevention is calling on all people who have purchased any salad from that facility to throw them out, even though the outbreak was last summer, according to an NBC News report.

The investigation began in September 2015. The source wasn’t identified until this month after a laboratory result came back. A total of 1,600 people are hospitalized each year from Listeria, and 260 people die annually. Listeria is most dangerous to the elderly, the very young, and people with compromised immune systems.

In a statement, the CDC said: “On January 21, 2016, Dole reported to CDC that it had stopped all production at the processing facility in Springfield, Ohio and is withdrawing all packaged salads currently on the market that were produced at this facility.”

The salads are bagged under the brand names of Dole, President’s Choice, Fresh Selections, Simple Truth, and Marketside. Customers can identify them by looking for the letter “A” at the beginning of the manufacturing code on the bag. The CDC is advising people not to eat these salads.

The cases happened in July, and there may have been well beyond 12 people who got sick. The 12 cases were serious enough to require hospitalization.

The CDC added: “State and local health departments are interviewing ill people about the foods they may have eaten or other exposures in the month before their illness began. Of five ill people who were asked about packaged salad, all five (100%) reported eating a packaged salad. Two (100%) of two ill people who specified the brand of packaged salad eaten reported various varieties of Dole brand packaged salad.”