(Reuters) – Walmart Inc on Wednesday became one of the last remaining major U.S. retailers to suspend the sale of over-the-counter heartburn medication containing ranitidine after the U.S. health agency flagged the presence of a probable cancer-causing impurity.

CVS Health Corp earlier this week said it would stop the sale of the medicines, while pharmacy chains Walgreens Boots Alliance Inc and Rite Aid Corp have also moved to remove the drugs off their shelves.

Some of the heartburn drugs containing the key ingredient ranitidine were found to have traces of the impurity, N-nitrosodimethylamine (NDMA), leading to Novartis AG halting global distribution of its versions of the popular drug commonly known as Zantac.

U.S. and European health regulators said last month they were reviewing the safety of ranitidine, while Canada requested makers of the drug to halt distribution as it gathers more information.

Walmart said it would stop the sale of Zantac, Equate and Member’s Mark brands.

(Reporting by Saumya Sibi Joseph in Bengaluru; Editing by Arun Koyyur and Maju Samuel)