Federal investigators are probing whether two drugmakers might have known about a probable carcinogen in Zantac and a similar generic but failed to share that information with the federal government.

The U.S. Department of Justice is investigating whether Sanofi and GlaxoSmithKline violated the False Claims Act by possibly failing to disclose the presence of NDMA (n-nitrosodimethylamine) in their Zantac and generic ranitidine heartburn products, according to a Law360 report. 

NDMA is classified as a “probable human carcinogen.” In April, the U.S. Food and Drug Administration requested that drug manufacturers immediately remove all prescription and over-the-counter ranitidine products from the market due to concerns the medications contained unacceptable levels of NDMA. 

Although GlaxoSmithKline is the original maker of Zantac, Sanofi currently holds the U.S. rights to the Zantac brand name. GlaxoSmithKline, along with other drug companies, sells generic ranitidine.

Sanofi, which is based in France, reported receiving notice of the investigation, along with requests for information, documents and FDA-related applications and communications, on June 6.

GlaxoSmithKline, which is based in England, reported receiving notice of the Justice Department investigation on June 18.

Information about Zantac and ranitidine investigations came from corporate filings with the U.S. Securities and Exchange Commission. 

The federal probe coincides with a New Mexico state lawsuit also filed in June alleging that Sanofi, GlaxoSmithKline and other ranitidine manufacturers violated the New Mexico Unfair Practices Act, False Advertising Act and public nuisance and negligence laws, as reported by Law360.