Walmart
A Walmart store is seen in Chinatown, Los Angeles, Jan. 16, 2016. Getty Images/AFP/MARK RALSTON

Around 21,220 pounds of frozen pizza was recalled by a Walmart Stores supplier in 11 states across the country over possible listeria contamination, the United States Department of Agriculture’s (USDA) Food Safety and Inspection Service (FSIS) and the company announced Thursday.

Vernon, California-based RBR Meat Company said about 6,700 pizzas sold under Wal-Mart’s Marketside brand were affected by the recall, which pulled the Marketside Extra Large Supreme Pizza after it emerged that it may have been “adulterated with Listeria monocytogenes,” according to FSIS.

The recall was issued for 50.6-oz. boxes containing single shrink-wrapped 16-inch pizzas labeled as “Marketside Extra Large Supreme Pizza,” produced on Feb. 23. The lot code of the recalled products is 20547, according to a statement by FSIS.

Read: Whole Foods Expands Its Recall Of Raw Cheese Over Possible Listeria Contamination

The USDA labeled it a Class I recall, which is defined as “a health hazard situation where there is a reasonable probability that the use of the product will cause serious, adverse health consequences or death.” The agency and Wal-Mart, however, said there were no known reports of illnesses linked to the pizzas.

Listeria contamination or Listeriosis is a serious infection that is caused by consuming contaminated food. The condition can be particularly dangerous for babies, pregnant women, older people, and others with weakened immune systems. According to the Centers for Disease Control and Prevention (CDC), those infected may notice symptoms like fever, muscle aches or gastrointestinal problems.

It can be treated with antibiotics and the FSIS said the accidental consumption of the contaminated products should be remedied by immediate medical care.

The recalled pizzas were available for sale in California, Colorado, Nevada, Washington state, Idaho, Montana, Oregon, Utah, Wyoming, Alaska, and Hawaii, according to the company. Consumers who purchased the recalled products were urged to not consume the pizzas and to return them to the store they were purchased from.