Twenty-two people "may have been exposed" to an anthrax sample sent to a U.S. Air Force base in South Korea and are being treated, a senior defense official told Fox News -- in the latest "precautionary measure" being taken after the Defense Department's "inadvertent" shipment of live anthrax samples. 

Those samples were sent to as many as nine states, as well as Osan Air Base in South Korea, over the course of a year. 

The 22 people now being treated in South Korea are in addition to the four people being treated for "post-exposure" in the U.S. after receiving anthrax spores. 

“There are no suspected cases of anthrax infection,” said Pentagon spokesman Col. Steve Warren.

Defense officials confirmed Wednesday that anthrax samples were mistakenly sent across the country. While the Pentagon is saying there is "no known risk to the general public," questions over which samples were live, and therefore dangerous, still remain.

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Of the 22 people in South Korea who might have been exposed, five are with the U.S. Air Force, 10 are with the U.S. Army, three are government contractors and four are civilians, the defense official said.  

The Pentagon said live anthrax, also known as Bacillus anthracis, was shipped to federal, private and academic labs between March 2014 and March 2015, apparently by accident, from a military lab at Dugway Proving Ground, Utah, as part of what was described as a "routine" research process. The shipments were supposed to include only inactive, or dead, anthrax when they were transferred. 

But on May 22, a private lab called the Edgewood Chemical Biological Center in Gunpowder, Md., informed the Centers for Disease Control (CDC) that they thought their samples contained live anthrax. The CDC then informed the Defense Department. 

According to the Associated Press, the government has confirmed the Maryland lab got live spores, and it is suspected the others did as well. A lab in Defense officials told  Fox News that the Virginia lab that received a portion of the anthrax was the Naval Surface Warfare Center in Dahlgren.When asked how many of the states that were sent anthrax received live samples, a defense official said that “out of an abundance of caution, it is safe to assume it’s all live." 

All samples are in the process of being collected by the Centers for Disease Control and Prevention. Precautions are being taken for potentially exposed workers in labs where the samples were sent.  The people treated for "post-exposure," for example, are being prescribed prophylaxis.  

"There is no known risk to the general public, and there are no suspected or confirmed cases of anthrax infection in potentially exposed lab workers," said Warren. "The DoD lab was working as part of a DoD effort to develop a field-based test to identify biological threats in the environment."  

After notified by the Army, each lab in the nine states has locked down the samples.The states that received the shipments are: Texas, Maryland, Wisconsin, Delaware, New Jersey, Tennessee, New York, California and Virginia. Warren said the DoD has also "stopped the shipment of this material from its labs pending completion of the investigation."

Fox News' Lucas Tomlinson contributed to this report.