The Centers for Disease Control and Prevention is investigating a shipment of anthrax mistakenly sent to labs in the United States and abroad from the Department of Defense, the agency said in a May 30 announcement.

The presence of anthrax was confirmed after a laboratory working with the DOD reported being able to grow live Bacillus anthracis bacteria, although an inactive agent was expected. The lab was working with the DOD to develop a diagnostic test to identify biological threats, the CDC reported.

The accidental shipment is not believed to pose a risk to the public, the CDC said. Samples are being sent to the CDC or Laboratory Response Network labs for testing, and CDC officials are performing onsite investigations at the laboratories involved.