(Reuters) – U.S. and European drug regulators said on Friday they are reviewing the safety of the widely taken heartburn drug ranitidine, commonly known by the brand name Zantac, after they found traces of a probable cancer-causing impurities in some versions of the medicine. The U.S. Food and Drug Administration said it had found traces of the impurity, called N-nitrosodimethylamine (NDMA), in some versions of drugs with ranitidine in them. Both the FDA and the European Medicines Agency said they will review the drug’s safety. The impurities in ranitidine were first flagged to the regulators by Valisure, an online pharmacy that tests the medication its sells for flaws. Valisure said in its report that it found the impurities in both Sanofi SA’s branded Zantac as well as generic versions of the drug. But the FDA would not confirm in which versions of the drug it had found the impurities, noting that it found quite different – and lower – amounts of NDMA in the drugs. NDMA is one of the impurities that has been found in blood pressure and heart failure medicines called Angiotensin II Receptor Blockers (ARBs). Regulators have been recalling those drugs since last year, and the FDA expanded its investigation of the impurities beyond that class of drugs last month. Janet Woodcock, director of the FDA’s Center for Drug Evaluation and Research, said in an interview that regulators around the world were considering requiring new testing during the manufacturing process to reduce contamination of drugs. “We’re going to have to be more vigilant,” Woodcock said. “I think you’ll see tests added at the appropriate point during the manufacturing.” Blood pressure and heart failure medicines such as valsartan, the generic version of Novartis AG’s (NOVN.S) Diovan, have been recalled by drugmakers such as Mylan NV (MYL.O), Teva Pharmaceutical Industries (TEVA.TA) and Novartis’ Sandoz, as the drugs have been found to contain probable carcinogens.