Sanofi recently announced that it would be expanding its recall of potentially contaminated Zantac due to low levels of carcinogens found in some of the heartburn medication.

The Oct. 18 recall announcement came over a month after the U.S. Food and Drug Administration (FDA) first announced the possible contamination of certain Zantac and generic ranitidine products. The products are reportedly contaminated with low levels of N-nitrosodimethylamine (NDMA).

“Sanofi is committed to transparency and will continue to communicate results with health authorities from the ongoing testing, and work with them to make informed decisions based on available data and evidence,” the drug manufacturer said in a statement.

Zantac and generic ranitidine products are histamine blockers which lower the acid created by the stomach. This can help with the symptoms of conditions such as gastroesophageal reflux disease (GERD), peptic ulcers, and more. Other histamine blockers such as Pepcid (famotidine) and Tagamet (cimetidine) have not been recalled.

The FDA warned of the possible Zantac contamination on Sept. 13 but didn’t call for patients to stop taking the medication at the time of the announcement due to the relatively low levels of NDMA. The agency is reportedly investigating the source of the NDMA contamination and determining the risk that patients may be at if they have taken contaminated ranitidine products.

NDMA is sometimes found in water, meats, dairy products, and vegetables as an environmental contaminant but can also be produced as a result of industrial processes. The chemical has reportedly been classified as a probably human carcinogen based on laboratory testing.

The FDA reportedly found “unacceptable levels” of NDMA in the Zantac products, but the levels were fairly low. The agency has rejected findings released by online pharmacy Valisure which found much higher levels of NDMA. According to the FDA, Valisure’s methods were problematic because they involved heating the samples. This can reportedly result in the production of NDMA, leading to higher test results.

According to the FDA, consumers can switch to another antacid medication if they are using over the counter versions of Zantac. Consumers who are taking prescription Zantac or ranitidine have been encouraged to speak with their doctor before making any changes to their medication.

Other Recalls of Contaminated Zantac

Although the FDA did not announce a recall immediately upon announcing the contamination, many major pharmacies took it upon themselves to pull contaminated Zantac from their shelves. Walgreens, Rite Aid, and CVS all stopped selling Zantac and ranitidine while the FDA investigates the issue. Consumers who purchased ranitidine medications from these retailers are reportedly able to contact them for a refund.

Recalls have also been initiated on a manufacturing level. Pharmaceutical companies such as Novartis’ Sandoz and GlaxoSmithKline have also recalled their ranitidine products due to the contamination risks. A recall has also been announced by Apotex, the company which makes the store branded versions of ranitidine products sold by Walgreens, Walmart, and Rite-Aid.

In other countries, regulators are also taking action to investigate the contamination. The European Medicines Agency is reportedly reviewing the drug and Health Canada has ordered a stop to all ranitidine sales while the contamination is investigated.