The problem of unintended shipments of potentially live anthrax spores over the past decade is worse than first believed, officials said Wednesday.

Officials said it’s possible that shipments were sent to more than four dozen laboratories in the U.S. and abroad. That’s about twice the estimate of last week.

The officials spoke on condition of anonymity because they weren’t authorized to discuss specifics by name. The Pentagon has repeatedly asserted that the mistakes posed no public health hazard. The Centers for Disease Control and Prevention is leading an investigation of the matter.

Details on the extent of the problem are expected to be presented at a news conference Wednesday by Robert Work, the deputy defense secretary. Last Friday Work ordered a comprehensive review of laboratory procedures associated with killing, or inactivating, live anthrax for shipment to labs for research and other purposes, including for calibrating biological threat sensors such as those used by a number of federal government agencies, including the Pentagon.

The scope of the problem has grown almost daily since the Pentagon first acknowledged it publicly last Wednesday.The initial focus was on procedures used at an Army laboratory at Dugway Proving Ground in Utah, which shipped live anthrax samples that it believed had been killed through the use of radiation. It remains unclear why well-established procedures for killing the spores apparently did not work, at least with some batches of the bacteria.

Among the government labs identified in recent days as having received the suspect anthrax were the Army’s Edgewood Chemical Biological Center in Maryland and the Naval Surface Warfare Center in Virginia, as well as a lab on the grounds of the Pentagon.

Officials said that the Edgewood lab sent some of the samples it had received from Dugway to other labs in the U.S.

On Tuesday, in its most recent update, the Pentagon said potentially live anthrax samples had been mistakenly sent to labs in California, Virginia, Texas, Tennessee, Utah, Massachusetts, Wisconsin, Maryland, New Jersey, New York, Delaware and Washington state. Also receiving suspect samples were labs in Australia, Canada and South Korea.

On Sunday, Defense Secretary Ash Carter told reporters while traveling in Asia that the mistaken shipments were an “unfortunate incident.” He said the Pentagon will make “sure that any public health consequences of this are avoided” and ensure that it never happens again.
The Centers for Disease Control of Prevention said last week that four people at labs in Delaware, Texas and Wisconsin were recommended to get antibiotics as a precaution, although they were not sick. U.S. officials at Osan Air Base in South Korea said 22 people were being treated for possible exposure there after word surfaced that an Osan lab was among the facilities that received suspect anthrax.

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