The U.S. Food and Drug Administration took more than 15 months to act on a whistleblower complaint it received about conditions at an Abbott Nutrition factory that was at the center of a nationwide shortage of infant formula, a new audit shows.

The Department of Labor received the email and three days later forwarded it to an FDA address specifically for such complaints. But one of several staff members charged with managing the FDA inbox at the time “inadvertently archived” the email in February 2021, and it wasn’t found until a reporter requested it in June 2022.

The episode is one of several that led the Department of Health and Human Services’ Office of Inspector General to conclude in a report Thursday that the FDA’s policies and procedures to address the issues at the Abbott plant were inadequate.