Another batch of live anthrax has turned up – this one from the same batch as samples sent to Australia from the Army’s Dugway Proving Grounds in Utah.

Defense officials tell NBC News the anthrax spores had been irradiated to kill them in 2008.

This does not necessarily mean the samples sent to the lab in Australia contained live anthrax spores, the officials say. They’ve been testing samples thought to have been inactivated ever since it turned out Dugway had sent potentially live spores to labs in nine states and an air base in South Korea.

Experts say it’s very difficult to inactivate a large batch of anthrax spores and say it’s a problem across U.S. labs. The Centers for Disease Control and Prevention, which is helping investigate the matter, says no member of the public is in danger and people who may have been exposed to the anthrax spores are taking antibiotics just to be safe.