In another incident involving listeria, a California farm on Thursday expanded a recall of chopped or shredded romaine lettuce to wholesale food distributors across 19 states and Alberta, Canada due to concerns about contamination with listeria.

True Leaf Farms of San Juan Bautista said no illnesses related to the recall had yet been reported.

The Thursday announcement, which came at the request of the U.S. Food and Drug Administration comes after an initial recall by True Farms on September 12 and 13 to a retail food service distributor in Oregon where 90 cartons were recalled. The latest action involves 2,500 cartons.

States involved in Thursday’s expanded recall are Alaska, Alabama, Arizona, California, Colorado, Connecticut, Florida, Illinois, Kentucky, Maryland, Minnesota, Missouri, Nevada, New York, Ohio, Oregon, Pennsylvania, Tennessee and Vermont.

In a separate incident arising in recent weeks, an outbreak of listeria in cantaloupes from Jensen Farms’ production fields in Granada, Colorado has killed at least 13 people and infected 72 across 18 states, according to the U.S. Centers for Disease Control.

Listeria is caused by eating food contaminated with the bacterium Listeria monocytogenes. It usually affects older adults, pregnant women, newborns and adults with weakened immune systems, according to the CDC.

Symptoms can include fever, muscle aches, diarrhea and other stomach problems.

Pregnant women may only experience a mild-flu-like illness; however the infection could lead to miscarriage, stillbirth, premature delivery, or life-threatening infection of the newborn.