— The Edgewood Area of Aberdeen Proving Ground was one of several facilities to which an Army bio-defense organization mistakenly sent samples of live anthrax, officials said Thursday, and a private commercial laboratory in Maryland was the first to report the problem to authorities.
Officials have not identified the private lab, and labs contacted by The Baltimore Sun said they didn't receive a sample or declined to comment.
None of the people that officials said are now being treated for possible exposure to the deadly bacterium are based in Maryland.
At least 26 people were being given antibiotics or vaccinations after the Army's Dugway Proving Ground in Utah sent the samples last month that ended up at 18 private and military laboratories in as many as nine states and South Korea, officials said.
No confirmed infections were reported, and officials insisted that the shipments of live anthrax spores around the country and halfway across the world posed no risk to the public.
The Pentagon said four civilians at commercial labs in Delaware, Texas and Wisconsin are being given antibiotics. Twenty-two other people are being treated or vaccinated at a U.S. military laboratory at Osan Air Base in South Korea.
Osan is home to a joint U.S.-Korean program that aims to boost bio-surveillance capabilities on the Korean Peninsula.
The Centers for Disease Control and Prevention said it was working with state and federal agencies to investigate how the anthrax samples were shipped from Dugway, a vast installation in southwest Utah where researchers try to build and test defenses against chemical and biological agents.
The anthrax samples were sent last month by commercial shipping companies to labs working to develop a new diagnostic test for anthrax, the CDC said.
The Army normally uses gamma radiation to render anthrax spores inactive before the material is sent to outside labs for research. But the private commercial lab in Maryland found that its sample contained live spores when it was cultured last Friday, and reported it to the CDC.
Officials said they are trying to determine what went wrong. Gen. Ray Odierno, the Army's chief of staff, said human error probably was not a factor.
Odierno told reporters Thursday that the problem might have been a failure in the technical process of inactivating the spores. In this case, he said, the process "might not have completely killed" the samples.
Officials said the government labs that received the suspect anthrax from Dugway were at the Edgewood Chemical Biological Center, at the Edgewood Area of Aberdeen Proving Ground, and the Naval Surface Warfare Center in Virginia.
The Edgewood center, which describes itself as the nation's principal research and development resource for non-medical chemical and biological defense, transferred some samples it received to other labs in the United States.
The Pentagon declined to identify the private labs involved, citing legal constraints.
The CDC said it had sent investigators to all 18 labs to determine whether the samples they received were live.
Officials said the nine states also include New York, California, Texas, New Jersey and Virginia.
"At this time we do not suspect any risk to the general public," the CDC said in a statement Thursday.
Infectious disease professionals expressed concern about a lack of oversight at Dugway.
"Clearly, this was a failure that never should have happened," said Dr. Amesh Adalja, a professor at the University of Pittsburgh and a member of the Infectious Diseases Society of America in Arlington, Va.
"Biomedical safety is essential when handling these sorts of agents," he said. "We need to get to the bottom of this and find out how it occurred, so it doesn't happen again."
Anthrax is an acute bacterial disease that can be fatal if not treated. It is not contagious but can be inhaled, ingested or transmitted through direct contact on the skin. Someone who is infected might not show symptoms for weeks.
Chemical weapons specialists from the Edgewood Chemical Biological Center last year destroyed Syria's stocks of the World War I blister agent sulfur mustard and the sarin precursor DF.
With the Middle Eastern nation in the midst of a civil war, they used a shipboard system developed in Maryland to destroy the weapons at an undisclosed location at sea.
Officials at Osan Air Base said that the anthrax bacteria it received for training purposes "might not be an inert training sample as expected" and was destroyed by hazardous materials teams Wednesday.
Col. Steve Warren, a Pentagon spokesman, said Thursday that the 22 personnel treated there included 10 members of the U.S. Army, five from the U.S. Air Force, four contract workers and three U.S. government civilians.
"None of the personnel have shown any signs of possible exposure," the air base said in a written statement.
The mistaken shipments were the latest in a series of incidents in which U.S. military mishandling of anthrax has set off a scare.
The head of the CDC's Bioterror Rapid Response and Advanced Technology Laboratory resigned last year after the lab failed to properly kill live anthrax samples and moved the material to an area where workers were not required to wear protective gear. Dozens of people were exposed, but no one was infected.
The nation's worst biological attack involved anthrax created in an Army facility in Maryland.
Less than a month after the attacks of Sept. 11, 2001, five envelopes containing dried anthrax spores were sent to several members of Congress and the media, sparking widespread fear of a debilitating terrorist attack.
At least 22 people contracted anthrax, and five died. The attack disrupted mail and other government services as experts struggled to decontaminate 35 post offices and mail rooms and several buildings on Capitol Hill.
The FBI concluded in 2008 that Dr. Bruce Ivans, a researcher at the U.S. Army Medical Research Institute of Infectious Diseases at Fort Detrick was responsible. He committed suicide before he was charged.
Baltimore Sun reporters Ian Duncan and Scott Dance and the Associated Press contributed to this article.