NEW YORK — Pharmacy chains CVS, Walgreens and Rite Aid and other retailers are pulling heartburn medication Zantac and its store-brand versions from their shelves after the Food and Drug Administration (FDA) warned it had detected low levels of a cancer-causing chemical in samples of the drug.

The actions follow the FDA’s release of a product alert that ranitidine might contain a low level of nitrosodimethylamine (NDMA), a probable human carcinogen.

Ranitidine is a histamine blocker used to prevent heartburn and treat conditions that cause an excess of stomach acid. Although the drug has not been recalled, the FDA said it is investigating the source of the contamination as well as the risk to users. The agency recommended that consumers who take the medication seek advice from their doctors and consider alternatives to the over-the-counter treatment.

Walgreens and CVS issued statements informing customers who bought the products that they could be returned for a refund. CVS said it would continue to sell other histamine blockers, including Pepcid, Tagamet and the generic equivalents famotidine and cimetidine.

Regional grocery store operator Hy-Vee announced it had suspended the sale of all Zantac and Topcare brand ranitidine products, a move the West Des Moines, Iowa-based company said was being taken “out of an abundance of caution.”

Paris-based Sanofi makes Zantac, but generic alternatives are also widely sold.

The New York Times reported that Apotex, which makes store-branded versions of Zantac for Walgreens, Walmart and Rite-Aid, recalled its ranitidine products last week. The newspaper also said that GlaxoSmithKline and Dr. Reddy’s Laboratories last month announced they had temporarily halted shipments of generic versions of ranitidine, and that Novartis had stopped distributing a prescription form of the drug.