U.S. defense officials say the problem of unintended shipments of potentially live anthrax spores over the past decade is likely worse than first believed.

The Pentagon says it has determined that possibly live anthrax was mistakenly sent to labs in Canada and Washington state, in addition to the numerous labs in the U.S. and abroad.

The Pentagon said Friday that the Army's mistaken shipments of live anthrax to research laboratories were more widespread than it initially reported, prompting the Defense Department's second-ranking official to order a thorough review.

The Centers for Disease Control and Prevention said Wednesday it is investigating what the Pentagon called an inadvertent shipment of live anthrax spores to government and commercial laboratories in as many as nine states.

Federal health officials say they have approved an infusible drug to treat patients who have been exposed to anthrax.

Health officials say that the head of the government lab which potentially exposed workers to live anthrax has resigned.

A second investigation has detailed additional safety problems at federal health laboratories in Atlanta, including the use of expired disinfectants and the transfer of dangerous germs in Ziploc bags.

At least 52 workers at the Centers for Disease Control and Prevention are taking antibiotics as a precaution because of a lab safety problem that may have accidentally exposed them to anthrax.

The Centers for Disease Control and Prevention says some of its staff in Atlanta may have been accidentally exposed to dangerous anthrax bacteria because of a safety problem at one of its labs.