The US military accidentally shipped at least one live anthrax sample across the country to a commercial lab in Maryland but there was no public health threat from the mishap, officials said Wednesday.

A Defense Department laboratory in Utah had "inadvertently" transferred the live anthrax sample to a commercial lab and government health authorities were still testing samples that had been shipped to other laboratories -- including one at a US military base in South Korea, defense officials said.

"There is no known risk to the general public, and there are no suspected or confirmed cases of anthrax infection in potentially exposed lab workers," Pentagon spokesman Colonel Steven Warren said in a statement.

The live anthrax sample, which had been transported by truck, was discovered by the commercial lab late on May 22 and the other laboratories were then informed, officials said.

But precise information about what had gone wrong, and how many labs might be affected remained unclear.

More than a dozen other government and commercial labs in at least nine states -- as well as a base in South Korea -- had received anthrax samples and authorities were trying to determine if there were other live spores transported.

One sample of anthrax was sent to a lab at Osan Air Base in South Korea, Warren said.

"The sample was destroyed in accordance with appropriate protocols," he said.

The Pentagon was assisting the US Centers for Disease Control and Prevention (CDC), which was investigating the incident.

Referring to the commercial lab in Maryland, the CDC said "although an inactivated agent was expected, the lab reported they were able to grow live Bacillus anthracis."

The CDC said in a statement the investigation is examining if other labs "also received other live samples, epidemiologic consultation, worker safety review, laboratory analysis, and handling of laboratory waste."

The Pentagon's announcement came less than a year since health officials faced severe criticism over a spate of safety lapses at CDC labs handling deadly pathogens, including anthrax.

- 'Dead' samples -

The Defense Department lab at Dugway Proving Grounds routinely transfers "dead" anthrax samples, which are inactivated through radiation, for scientific research, officials said.

The lab was working on a project "to develop a field-based test to identify biological threats in the environment," Warren said.

As a precaution, the Defense Department "has stopped the shipment of this material from its labs pending completion of the investigation," he said.

The lethal anthrax disease is spread by spores and has been used for bioweapons programs in the United States and elsewhere. Washington long ago scrapped its bioweapons effort as part of an international treaty, which the United States ratified in 1975.

US government laboratories came under fire last year over reports of sloppy management of deadly bacteria.

As a result, health officials suspended the shipment of potentially dangerous pathogens from government labs in Atlanta and the CDC shut down two of its laboratories, including one implicated in the mishandling of anthrax samples.

Lawmakers have demanded stricter oversight of the government labs.

Investigators from the Agriculture Department last year found anthrax was stored in unlocked refrigerators in an unrestricted corridor, and that dangerous materials were transferred using resealable plastic bags.