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LOUISVILLE, Ky. (WDRB) -- A drug prescribed to millions of Americans with diabetes is being investigated for possible carcinogenic contaminants.

The U.S. Food and Drug Administration is looking into whether some Metformin sold in the U.S. is contaminated with NDMA, which is a contaminant linked to some cancers.

The FDA said in a release that N-Nitrosodimethylamine or NDMA "is a common contaminant found in water and foods including cured and grilled meats, dairy products and vegetables. Everyone is exposed to some level of NDMA." Regulators say when ingested in small levels it does not cause any harm.

"While we are aware that some regulatory agencies outside the U.S. may be recalling some Metformin drugs, there are no Metformin recalls affecting the U.S. market at this time," according to a statement from Janet Woodcock, M.D., the director for the Center for Drug Evaluation and Research.

Metformin is a prescription drug used to control high blood sugar in patients with type 2 diabetes. Patients should continue taking the drug to keep their diabetes under control.

NDMA is the same contaminant that forced recalls of blood pressure and over-the-counter heartburn medications over the past year.

The FDA says it will continue to investigate the source of the impurities, but they note that there may be additional reasons for increased NDMA levels in Metformin.

"Previously, we found the source of NDMA can be related to the drug’s manufacturing process or its chemical structure or even the conditions in which they are stored or packaged," according to the statement.

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