The plant in Kalundborg, Denmark lacked information intended to show that water used in drug production was adequately controlled for certain microorganisms, according to a US Food and Drug Administration inspection report from March. The manufacturing process was being used at the plant to make a once-weekly form of insulin, a Novo spokesperson said.

The FDA earlier questioned the process when it denied approval of the product, the spokesperson said. The company remains in contact with the FDA and doesn’t expect to resolve the issue this year.

Novo has been racing to boost supplies of its drugs for obesity and diabetes after initially underestimating demand while overcoming issues at a contract manufacturer. The Kalundborg site, where a fire was also reported earlier this year, plays a key role in Novo’s long-term plan to satisfy demand. It is one of two places in the world where Novo makes semaglutide, the active ingredient in the two blockbusters. 

Novo’s other site that makes semaglutide is in North Carolina. That plant was cited by the FDA last September for failing to properly investigate bacterial contamination.

While new obesity drugs are driving Novo’s growth, insulin has been the company’s core product for a century. People with type 1 diabetes depend on injected insulin to regulate blood sugar because they don’t produce enough of the hormone naturally.

Novo’s American depositary receipts were little changed at the close of trading in New York. 

(Updates with company comment in second paragraph, additional information in fourth.)