Celltrion Inc. received a warning letter from the U.S. Food and Drug Administration for violations in its manufacturing plant.

The regulator cited a lack of written procedures, employee training and certain documentation, among others, at Celltrion's facility in Incheon, South Korea. The FDA listed eight observations from seven inspections of the site in July.

The company said it has provided a comprehensive response to address the FDA's concerns and expects the outstanding observations to be lifted shortly.

In January, Celltrion also received a warning letter for issues at its Incheon facility. In April, the FDA rejected the company's application to gain marketing approval for two biosimilar drugs, citing that warning letter.