The US military said on Friday it discovered even more suspected shipments of live anthrax than previously thought, both in the United States and abroad, and ordered a sweeping review of practices meant to inactivate the bacteria.
The Pentagon said a total of 11 states, two more than it first acknowledged, received "suspect samples," as did Australia and South Korea. It had previously only identified a foreign shipment to a US air base south of Seoul.
"There is no known risk to the general public and an extremely low risk to lab workers," the Pentagon said in a statement.
Still, in a sign the Pentagon was still coming to grips with the extent of the problem, it advised all laboratories for now to stop working with any "inactive" samples sent from the Defense Department.
To date, the United States has acknowledged that four US civilians have begun taking preventive measures that usually include the anthrax vaccine, antibiotics or both.
Twenty-two people at the base in South Korea were also given precautionary medical measures although none of them has shown signs of exposure, officials said.
The suspected live samples identified so far all appear to trace back to a US Army base in Utah, the Dugway Proving Ground, one of the military labs responsible for inactivation and shipping of biological material.