The FDA sent a warning letter on August 12 to the drugmaker’s Sandoz generic unit about a failure to properly validate the manufacturing process for a copycat version of AstraZeneca’s Toprol XL, a blood pressure medication, which it makes a North Carolina plant.

“We question the continued distribution of this product until better process controls are implemented and process validation is completed,” the FDA wrote to Sandoz ceo Bernard Hampl. “We are also concerned that the problems noted in the metoprolol validations could be indicative of problems and poor decisions made with other product validations.”

A Novartis spokesman tells Reuters the FDA’s concerns were “primarily about documentation and validation. We are working together with the FDA to solve the problem.”