One person has died and 12 others are hospitalized after eating packaged salads linked to a Listeria outbreak.

The Centers for Disease Control and Prevention said Friday that the salads were sold under a variety of names and came from a processing facility in Springfield, Ohio, run by Dole.

The dozen who were hospitalized come from six states — Massachusetts, Michigan, New Jersey, New York, Pennsylvania and Indiana. The fatality was in Michigan. Reports about these infections started coming in July.

An investigation began in September, the CDC said, but the source of the infections was unknown until this month when lab tests confirmed listeria in salads collected from the Springfield facility.

The CDC is warning people not to eat salads packaged under the name Dole, Fresh Selections, Simple Truth, Marketside, The Little Salad Bar and President’s Choice. The salads are sold to restaurants as well. If you have one of these packaged salads in your fridge look for the letter “A” at the beginning of the manufacturing code. Those are the ones you want to throw away.

On Thursday, Dole told the CDC it has stopped all production at the Springfield facility and is pulling all packaged salads made at this facility still on the market. There is no evidence that salads made at other facilities are contaminated with the bacteria, the CDC said.

Listeria, known by its scientific name of Listeria monocytogenes, is the bacterium that causes listeriosis, an infection that affects the gastrointestinal tract. This serious infection can cause temporary problems such as a high fever, abdominal pain and diarrhea, headaches, stiffness and nausea. It can be particularly dangerous for pregnant women, the elderly, children and anyone with a weak immune system due to a chronic condition. Some infections are so serious they can cause death.

The CDC estimates there are about 1,600 illnesses and 260 deaths per year due to listeriosis infections.