DWithers/iStock Unreleased via Getty Images A laboratory that five years ago discovered the presence of the chemical NDMA in the heartburn drug Zantac has filed a whistleblower lawsuit against GSK ( NYSE: GSK ). The British drugmaker, along with others that marketed the drug, are already facing tens of thousands of lawsuits from Zantac users who say the medication caused cancer. The new lawsuit was brought by Connecticut-based Valisure, which engages in independent quality assurance of drugs.

In 2019, the company found the presence of NDMA , a known carcinogen, in every batch of Zantac (ranitidine) and generics during routine testing and notified the U.S. FDA in June of that year.

In September 2019, it submitted a petition to the agency asking that all medications with ranitidine be recalled. In 2020, ranitidine was pulled from the market. The lawsuit, filed on Monday in a Philadelphia federal court, and reported by Bloomberg , alleges that GSK ( GSK ) knew about the cancer risks associated with Zantac but hid them, all while federal government health services, such as Medicare and Medicaid, covered the drug.

A GSK spokesperson told the news service that there is "no consistent or reliable evidence" that Zantac increases cancer risk. More on GSK GSK Trades At Low Price Multiples, But Its Pipeline Needs To Improve Novo Nordisk, J&J lead R&D rankings in big pharma: report GSK to sell entire Haleon stake GSK plc (GSK) TD Cowen 44th Annual Health Care Conference (Transcript) GSK .