The Food and Drug Administration has announced a voluntary recall of a widely prescribed blood pressure medication made in China, reviving fears about the safety of imported drugs.

Three companies that sell the generic drug, valsartan, in the United States agreed to recall it after the F.D.A. said it might be tainted by N-nitrosodimethylamine (NDMA), considered a probable human carcinogen. The agency is still investigating, but said the contamination was believed to be related to changes in the way that valsartan was manufactured.

All of the valsartan that is being recalled was made in China by the same company, Zhejiang Huahai Pharmaceutical Co. Ltd. It is distributed in the United States by three companies: Major Pharmaceuticals; Teva Pharmaceutical Industries, Ltd.; and Solco Healthcare. Solco, which is owned by Huahai Pharmaceutical, had about 45 percent of the market in 2017, according to John Brito, of Fore Pharma, the market research firm.

“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,” said Dr. Janet Woodcock, director of the F.D.A.’s Center for Drug Evaluation and Research. “That is why we’ve asked these companies to take immediate action to protect patients.”