Pfizer (PFE.N) voluntarily recalled five batches of its Accupril blood pressure pills on Friday after the discovery of high amounts of a possible cancer-causing chemical in the medication.

The manufacturer said that it was unaware of any adverse event reports associated with the recalled batches, which were supplied in the United States and Puerto Rico between December 2019 and April 2022. Pfizer Canada similarly recalled all lots of three Accupril dosages on Thursday after determining that the same contaminant was present at unsafe levels. Pfizer said that there was no immediate danger to patients who were taking the drug that included the chemical, nitrosamine. While nitrosamines are naturally occurring in water and food, prolonged exposure over tolerable levels may raise the risk of cancer. Pfizer also withdrew several batches of another blood pressure medication, Accuretic, and two approved less expensive generic equivalents last month owing to the presence of a probable carcinogen.