The Food and Drug Administration on Thursday alerted doctors and patients to a voluntary recall of over-the-counter ranitidine in 75 mg and 150 mg tablets. On Saturday, CVS Pharmacy joined Walgreens, Walmart and Rite-Aid as chains that have suspended the sale of Zantac, as well as CVS Health-brand ranitidine products.

The FDA said ranitidine products may contain a possible human carcinogen and cause cancer.

Ranitidine is typically used to treat heartburn, acid ingestion and sour stomach. 

The FDA is advising consumers to seek other over-the-counter products to treat these symptoms and stressed on its official site that not all ranitidine medicines in the U.S. are being recalled and that consumers do not need to stop taking any and all ranitidine products. 

The pills involved in the recall are produced by Toronto-based Apotex Corp. and include some products sold as generic versions of Zantac. CVS, which has roughly 10,000 locations, says they will continue to sell similar over-the-counter products including Pepcid, Tagamet and other equivalents.

According to the recall, these products may contain low levels of N-nitrodimethylamine (NDMA), a nitrosamine impurity believed to be a probable carcinogen. NDMA has been found to possibly cause cancer in humans based on lab studies. It is considered to be an environmental contaminant and has been found in meats, vegetables and dairy products.

“FDA is continuing to test ranitidine products from multiple manufacturers and assess the possible effect on patients who have been taking ranitidine,” the federal agency said in a statement. “FDA has asked ranitidine manufacturers to conduct laboratory testing to examine levels of NDMA in ranitidine and to send samples of ranitidine to the agency to be tested by our scientists.”

This recall comes after Canada and France announced Zantac recalls and after the FDA and the European Medicines Agency (EMA) on Sept. 13 published their joint decision to review the presence of NDMA in medicines containing ranitidine.