The FDA should urge hospitals to make sure they’re using registered compounding pharmacies, government auditors say in a new report.

HHS’ Inspector General found that compounding pharmacies overwhelmingly comply with federal safety and quality standards but that the FDA has to do a better job of stressing the importance of registered compounders for America’s hospitals. Unregistered compounders may “pose a public health threat,” the auditors wrote.

“Hospitals are the frontline of patient safety and safely compounded drugs are necessary for effective patient care,” the Inspector General said.

The auditors provided a list of unregistered compounders to the FDA and officials have already begun inspections, the agency told the Inspector General.