FILE PHOTO - A view shows the U.S. Food and Drug Administration (FDA) headquarters in Silver Spring, Maryland August 14, 2012. REUTERS/Jason Reed/File Photo

NEW YORK (Reuters) - Additional shortages of blood pressure drugs in the United States are possible following recent recalls related to traces of a probable carcinogen found in some versions a particular class of hypertension medicines, the U.S. Food and Drug Administration said on Friday.

The drugs, including valsartan, belong to a class of widely-used medicines for treating high blood pressure called angiotensin II receptor blockers, or ARBs. Valsartan is the generic of Novartis’ Diovan.

The FDA also said it may have identified the root cause of the potentially cancer-causing impurities but that it is still investigating.

The recalls began last summer after the FDA was informed that ingredients used by Chinese manufacturer Zhejiang Huahai Pharmaceuticals Co (Huahai) to produce valsartan contained the impurities. The FDA later halted all imports from one of Huahai’s factories.

Other manufacturers have also had to recall valsartan after the impurities were found in their versions of the drug as well. It is currently listed as in shortage by the FDA.

Some generic versions of other ARBS, such as losartan and irbesartan, have also been recalled. The most recent recall was announced earlier this week.

The agency said that it determined that the impurities “may be generated when specific chemicals and reaction conditions are present in the manufacturing process” and “may also result from the reuse of materials, such as solvents.”

The reuse of solvents is an accepted practice in the industry, but manufacturers are generally expected to ensure that reused materials meet certain safety standards.