EU regulators flagged 18 percent of inspected biologics and nine percent of inspected drugs for scientific or regulatory problems in the two decades since European regulators began inspecting drugs and medicines, the European Medicines Agency said in a new report.

The agency says it has conducted 700 product inspections since the late 1990s, with most of the issues flagged by inspectors resolved by having manufacturers revamp their controls.

The higher level of problems found in biologics “might be linked to the fact that the products are more complex and as a consequence the test methods involved are usually more sophisticated and sensitive,” the agency said.

The inspection regime has led to four batch recalls: One in 2006, when there were problems with human growth hormone (somatropin) injections, one in 2009 because of impurities in veterinary antibiotics, and two in 2017, when there were problems with Zoledronic acid and Meloxicam generic drugs.