Image copyright EPA Image caption The Pentagon said that it accidentally sent shipments of live anthrax bacteria from the Dugway Proving ground facility (pictured)

The US military has ordered a review of how it handles anthrax after discovering more cases of live samples being accidentally sent to labs.

Live anthrax samples were believed to have been sent to a total of 24 labs, in 11 US states as well as South Korea and Australia, the Pentagon said.

The Pentagon says that there is no known risk to the general public.

Experts in biosafety have heavily criticised the lapse and called for improved precautions.

Symptoms of anthrax exposure include skin ulcers, nausea, vomiting and fever, and can cause death if untreated.

'Live spores'

News of the live shipments first emerged on Wednesday, as the US said it had accidentally shipped live anthrax spores from Utah to labs in Texas, Maryland, Wisconsin, Delaware, New Jersey, Tennessee, New York, California and Virginia, as well as an air base in South Korea.

Those shipments took place between March 2014 and April 2015, a US official said, according to Reuters.

On Friday, the Department of Defense said it had identified "additional inadvertent live anthrax shipments", including a suspect sample sent to Australia from a batch of anthrax from 2008.

It is not clear when that sample was shipped to Australia.

The military has ordered all of its labs that have previously received inactive anthrax samples to test them. In addition it is advising all labs to cease working with these samples until told otherwise.

Media playback is unsupported on your device Media caption The military used commercial carriers to deliver what it thought was inert anthrax to research laboratories, as Steve Evans reports

The samples sent out were supposed to have been deactivated or dead but instead contained "live spores."

The Centers for Disease Control and Prevention (CDC) is leading the investigation into the incident.

Twenty-two military personnel in South Korea received preventive treatment this week after being possibly exposed to the sample sent to Osan Air Base.

The personnel at the South Korean base might have come into contact with the anthrax sample during a "training event", the US military said, but so far none had shown "any signs" of exposure.

However, they were given "appropriate medical precautionary measures to include examinations, antibiotics and in some instances, vaccinations".

What is anthrax?

Image copyright AP Image caption Workers must wear protective clothing

Anthrax bacteria live primarily in inactive spores and are found naturally in the soil, but people can ingest or inhale spores, which can make the anthrax active.

Not all will be sickened when exposed to anthrax but left untreated, anthrax illness can turn very serious or lead to death.

A blood culture test is used to confirm anthrax exposure.

Anthrax entered the US national consciousness in 2001, when shortly after the 9/11 attacks, letters containing powdered anthrax arrived at news organisations and the offices of US senators. Twenty-two people were sickened and of those, five people died.

Sources: FBI Anthrax investigation; CDC, San Francisco Department of Public Health