HAI PHONG, Vietnam (Reuters) - U.S. Defense Secretary Ash Carter is "keeping in close touch" with events surrounding the discovery that live samples of the deadly anthrax bacteria had been sent by a Defense Department laboratory to 11 U.S. states and two countries.
"This is obviously a very unfortunate incident," Carter told reporters while visiting the port city of Hai Phong in Vietnam. He said the department was working to limit any public health consequences and make sure "it never happens again."
He also said it was important to "find out who's responsible and hold them accountable."
"I'm keeping in close touch with it," Carter said.
The U.S. 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 received "suspect samples", as did Australia and South Korea.
"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 U.S. 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 U.S. Army base in Utah, the Dugway Proving Ground, one of the military labs responsible for inactivation and shipping of biological material.
The Pentagon said Frank Kendall, undersecretary of defense for acquisition, technology and logistics, would lead the Pentagon's review of the incident, which included an examination of procedures for inactivating anthrax.
The U.S. Centers for Disease Control and Prevention has already begun an investigation.
(Reporting by David Alexander and Phil Stewart; Editing by Rosalind Russell)