Shares of Paris-based pharmaceutical giant Sanofi (SNY) - Get Report were under pressure on Friday after the U.S. Food and Drug Administration issued a statement saying its heartburn medication Zantac includes an impurity that could cause cancer.

Sanofi fell by nearly 2% in early trading in New York before recovering. At last check, American depositary receipts of Sanofi were up slightly to $43.82.

The FDA said it has learned that "some ranitidine medicines, including some products commonly known as the brand-name drug Zantac," contain low levels of N-nitrosodimethylamine (NDMA), which is classified as a "probable human carcinogen" based on lab tests. "NDMA is a known environmental contaminant and found in water and foods, including meats, dairy products, and vegetables," the FDA stated. 

The agency isn't calling for consumers to stop taking ranitidine "at this time," but said people taking it in prescription form should talk to their doctor and those taking it over-the-counter "could consider" using other medicines for their condition.

The FDA said it has been investigating NDMA in blood pressure and heart failure medicines since last year and is evaluating whether low levels pose a risk to patients. In the case of Angiotensin II Receptor Blockers (ARBs), the FDA has recommended numerous recalls after discovering "unacceptable levels of nitrosamines."

"Sanofi takes patient safety seriously, and we are committed to working with the FDA," the company said in a statement."Zantac OTC (over the counter) has been around for over a decade and meets all the specified safety requirements for use in the OTC market."