The military accidently shipped live anthrax samples around the U.S. under "less stringent" safety protocols, according to officials. A lab in Maryland that received the samples prompted a review to determine if and where other live anthrax samples had been shipped.

The shipments, thought to be dead, were shipped under less rigorous conditions than the live agent protocol.

NBC News reported that the anthrax was sent via FedEx.

Experts say there is no risk to the public from shipping the anthrax, but four workers have been put in treatment because they actually handled the samples.

Pentagon spokesman Col. Steve Warren said that one of the samples was also sent to the Joint United States Forces Korea Portal and Integrated Threat Recognition Program at Osan Air Base in South Korea. "The sample was destroyed in accordance with appropriate protocols," Warren said.

The Center for Disease Control were also investigating the mishap along with the Defense Department.

"CDC is working in conjunction with state and federal partners to conduct an investigation with all the labs that received samples from the DOD," Jason McDonald, a CDC spokesman said. "The ongoing investigation includes determining if the labs also received other live samples, epidemiologic consultation, worker safety review, laboratory analysis and handling of laboratory waste."