The U.S. Food and Drug Administration (FDA) said on Monday it had issued warning letters to Olympus' units pertaining to a category of devices known as endoscopes, citing violations at its facilities.

Olympus said it was making changes to the quality systems at its facilities.

Responses to each warning letter have been submitted to FDA, and the actions to fix the issues is progressing, a company spokesperson said in an emailed response late Wednesday.

(Reporting by Raghav Mahobe in Bengaluru; Editing by Shailesh Kuber)