Washington (AFP) - As many as 22 people in South Korea and four US lab workers may have been exposed to anthrax after the American military accidentally shipped out at least one live sample, officials said.The four lab employees were undergoing medical treatment as a precaution after the military sent the sample inside the country to a commercial lab in Maryland, US officials said Wednesday.As many as 22 personnel may have been exposed to anthrax during a laboratory training exercise at the US Osan Air Force Base in South Korea using samples shipped from the same batch, a military statement said Thursday.In addition to the military base in South Korea, more than a dozen other government and commercial labs in nine US states had received samples from the accidental shipment, officials said.All of the samples had been irradiated in March last year at a military lab in Utah and were supposed to be "dead."But on Friday, a private firm in Maryland notified authorities that its sample was still active, setting off an urgent review of all material sent out to other labs, defense officials said.Four people at three different companies that had "worked with the live anthrax" were receiving post-exposure treatment as a precaution. - 'No risk' to public - The Pentagon and health officials said the incident posed no threat to public health."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," Pentagon spokesman Colonel Steven Warren said in a statement.The Osan Air Force Base also stressed that there was "no risk" to the public.It said an alarm had been sounded after it was discovered that the bacteria being used in a laboratory training exercise might not have been an inert sample."Twenty-two personnel may have been exposed during the training event," the statement said, while adding that none had shown any exposure symptoms.The sample was being used in a self-contained "laboratory environment" on the base."Hazardous material teams immediately cordoned off the facility, decontaminated it...