The FDA is recalling several medications used to treat high blood pressure and heart failure after a substance that could cause cancer was discovered in them.

The impurity N-nitrosodimethylamine (NDMA) was found in the products. The FDA said the reason the NDMA was in the medications is “thought to be related to changes in the way the active substances was manufactured.”

The recalled medications have valsartan in them. The ingredient was supplied by a third party.

“Not all valsartan-containing medicines distributed in the United States have valsartan active pharmaceutical ingredient (API) supplied by this specific company,” the FDA explained. “The supplier has stopped distributing its valsartan API and the FDA is working with the affected companies to reduce or eliminate the valsartan API impurity from future products.”

Here are the recalled medications and the companies that produced them:

“We have carefully assessed the valsartan-containing medications sold in the United States, and we’ve found that the valsartan sold by these specific companies does not meet our safety standards. This is why we’ve asked these companies to take immediate action to protect patients,” Janet Woodcock, M.D., director of the FDA’s Center for Drug Evaluation and Research, said.

Patients taking these prescriptions to treat serious medical conditions should keep taking them until they have a replacement product. You should also follow the recall instructions provided by the specific company.

To determine whether a specific product has been recalled, look at the drug name and company name on the prescription bottle’s label. If you are unable to find that information on the label, contact the pharmacy from which you purchased your medication. Anyone taking the medication should also call their doctor or pharmacist to figure out what medication they should take.