According to the FDA, an impurity called N-nitrosodimethylamine, or NDMA, was found in the recalled drugs.
The FDA called NDMA a "probable human carcinogen."
"The presence of NDMA was unexpected and is thought to be related to changes in the way the active substance was manufactured," the FDA said in its Friday announcement.
The recall doesn't include all products containing valsartan.
Valsartan medications made by Major Pharmaceuticals, Solco Healthcare and Teva Pharmaceuticals Industries Ltd. are being recalled, along with valsartan/hydrochlorothiazide (HCTZ) from Solco Healthcare and Teva Pharmaceuticals Industries Ltd.
"We have carefully assessed the valsartan-containing medications sold in the United States, and we've found that the valsartan sold by these specific companies does not meet our safety standards. This is why we've asked these companies to take immediate action to protect patients," said Janet Woodcock, M.D., director of the FDA's Center for Drug Evaluation and Research.
The FDA said users of the recalled drugs should continue taking them until they've found a replacement and consult their health care professionals to discuss plans for their ongoing treatment.