The United States military has mistakenly shipped live anthrax samples to laboratories in nine states across the country and even to a US military base in South Korea, the defence department has confirmed.

CNN reported on Wednesday that a laboratory based in Maryland was among the recipients of the live anthrax samples.

Live anthrax samples were also accidentally delivered to a laboratory in Dugway, Utah.

Col. Steve Warren, US Defence Department spokesman, meanwhile confirmed that live anthrax samples were also sent by the military 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.

NBC News said in a separate report that the anthrax samples were sent via FedEx. The courier delivery service's spokesman, Jim McCluskey, however did not confirm this report.

The inadvertent shipping of the live anthrax samples has prompted the defence department to subject four of its employees in the US and 22 others overseas to post-exposure treatment.

The Defence Department said these employees have been given "appropriate medical precautionary measures to include examinations, antibiotics and in some instances, vaccinations."

"None of the personnel have shown any signs of possible exposure," Warren said.

When anthrax is released into the air, it triggers a deadly illness called inhalation anthrax. This took place in 2001 when anthrax sent through the US mail to government and media targets killed five people.

The anthrax, which was initially sent from a Utah military lab, was intended to be shipped in an inactive state as part of efforts to develop a field-based test to identify biological threats, the Pentagon said.

"Out of an abundance of caution, (the Defense Department) has stopped the shipment of this material from its labs pending completion of the investigation," Warren said.

The Center for Disease Control and Prevention (CDC) has launched an investigation on the accidental shipping of the anthrax samples.

CDC spokeswoman Kathy Harden said the destroyed anthrax samples inadvertently sent by the US military will be transferred under tight security to the CDC "for further testing."

Officials from CDC have also been sent to the laboratories that received the anthrax samples to do on-site investigations.

The anthrax bacteria, Bacillus anthracis, causes an acute diseases which can be transmitted through contact.