The Food and Drug Administration or FDA has announced recalls of two more lots of ranitidine after detecting probable carcinogen in the heartburn drug.

The FDA said that Denton Pharma Inc had recalled several batches of unexpired ranitidine tablets due to the possible presence of N-Nitrosodimethylamine NDMA, NBC reported on Friday.

Appco Pharma also recalled batches of ranitidine because of the potential presence of NDMA. The recalled lots have an expiration date of April or May 2021.

The World Health Organisation has classified that substance, N-Nitrosodimethylamine or NDMA, as a “probable human carcinogen”.

None of the recalled lots has been associated with any injuries or adverse events, according to the NBC.

In an announcement last Wednesday, the FDA also said that the drug company Mylan has recalled three lots of another antacid, nizatidine, which were also found to contain trace amounts of NDMA.

Those capsules, in 150mg and 300mg strengths, were manufactured by Solara Active Pharma Sciences Limited.

Nizatidine is used for short-term treatment of stomach ulcers as well as heartburn caused by gastroesophageal reflux disease, the FDA wrote on its website.

The FDA said it has not received any reports of injuries associated with taking the medications.

It’s unclear whether such trace amounts of the carcinogens would cause harm when taken as directed.

FDA testing of recalled ranitidine detected NDMA levels similar to the levels found in grilled and smoked meats, the NBC said.

Other heartburn medications, such as famotidine (Pepcid), cimetidine (Tagamet), esomeprazole (Nexium), lansoprazole (Prevacid) and omeprazole (Prilosec) have not tested positive for signs of NDMA, it reported citing federal regulators.