The Federal Government needs to explain how a US military lab was able to send live anthrax to Australia, Senator Nick Xenophon says.

The call for an explanation came after an investigation of a US military facility's mistaken shipments of live anthrax bacteria turned up another live sample, this one from a 2008 batch sent to Australia.

The Pentagon has revealed 24 labs in the United States and one each in Australia and South Korea received suspect anthrax samples.

Analysts say the disclosure suggests the possibility of a broader problem among anthrax samples meant to have been made inactive at the US Army's Dugway Proving Ground in Utah.

Little is known about the sample sent to Australia, including the type of laboratory that received it.

In Adelaide on Saturday, Senator Xenophon said that was "incredibly alarming" and called for an investigation as a "matter of urgency".

"If the Australian Government can put a big effort in terms of quarantine and biosecurity in relation to Johnny Depp's dogs, you think they would pull out all stops," he said.

"Something that can be used a a chemical weapon, a weapon of mass terror ... there needs to be a full explanation from the Government."

Foreign Minister Julie Bishop today said an investigation was underway.

"We are assured by the US military that there is no risk to public health, that there is no risk as a result of this," Ms Bishop said.

Defence said it would conduct tests on the sample to determine if it contained any live spores.

A statement from Defence said the sample was sent to the Defence Science and Technology Organisation, which conducts research into chemical and biological warfare agents.

It said the results of tests will be provided to the Australian Government and the United States.

Investigation 'may take some time'

A US defence official, speaking on condition of anonymity, said the sample was tested after the latest disclosure as part of the ongoing investigation into the handling of anthrax samples.

A spokesperson from the Australian Department of Agriculture said the allegations were being assessed and an investigation undertaken to determine the circumstances of the alleged arrival, including whether it did arrive.

"Given that this relates to a potential import from 2008, this may take some time to complete," the spokesperson said.

"The Australian Government is working with the US government in the course of this investigation.

"There is a negligible risk to human health."

Suspected live samples sourced to Dugway have already been traced going to 11 US states and a US air base in South Korea over a period from March 2014 to April 2015 before being discovered this month.

Sorry, this video has expired Ben Knight talks to Weekend Breakfast ( Ben Knight )

The US military says there are no known suspected infections or risks to the general public.

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.

The US Centres for Disease Control and Prevention has begun an investigation.

It was unclear how many other samples from Dugway have been tested or what the results of those tests are.

On Thursday, the US army's top general said human error probably was not the cause, saying preliminary information suggested US personnel at Dugway appeared to correctly follow official procedures.

The Pentagon was more cautious on Friday.

"There is an ongoing investigation and we need to let this develop," Pentagon spokesman Colonel Steve Warren said.

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ABC/Reuters