The U.S. Food and Drug Administration released a warning letter issued to Zhejiang Huahai Pharmaceutical Co. Ltd. (ZHP), in Linhai, Taizhou Zhejiang China, the manufacturer of the active pharmaceutical ingredient (API) found in valsartan that is the subject of an ongoing FDA investigation into probable cancer-causing impurities in certain commonly prescribed heart medicines. The letter outlines several manufacturing violations at ZHP’s Chuannan facility, including impurity control, change control and cross contamination from one manufacturing process line to another. The warning letter is another step forward in the ongoing investigation. The agency is still looking into the root cause of the impurity.