The US military is accused of a “serious breach of trust” in its obligations to protect civilians after admitting it accidentally sent more live samples of anthrax to laboratories than previously thought.
The deadly spores are supposed to be made harmless before being shipped out, but live samples were sent to 24 labs in 11 US states – as well as to South Korea and Australia.
The Pentagon previously said nine US states and an American air base south of Seoul had received “suspect samples”.
It said there is “no known risk” to the general public and an “extremely low risk” to lab workers.
However, in a sign the US military is still coming to terms with the extent of the problem, it advised all labs to stop working with any “inactive” samples sent from the Defense Department.
To date, it has revealed that four lab workers in Texas, Delaware and Wisconsin are taking preventive measures that usually include the anthrax vaccine, antibiotics or both.
At Osan air base in South Korea, 22 military and civilian personnel have also been given precautionary medical measures.
The live samples all appear to have come from Dugway Proving Ground, a US Army base in Utah responsible for inactivation and shipping of biological material.
The shipments took place between March 2014 to April 2015 before being discovered earlier this month.
On Friday, US officials said the suspect samples sent to Australia came from a 2008 batch from Dugway, which was meant to be made inactive or “dead”.
It is not clear when samples were sent out or where the samples were sent, other than Australia, officials said.
“We are still trying to figure out where the samples were sent,” a source told AFP news agency.
The discovery has raised alarms in Congress, with Senator Bill Nelson calling it a “serious breach of trust” in the US Army’s obligation to keep Americans and troops safe.
Frank Kendall, undersecretary of defence for acquisition, technology and logistics, is leading the Pentagon’s investigation, including an examination of procedures for inactivating anthrax.
The US Centers for Disease Control and Prevention (CDC) – one of the government’s top civilian labs – has also launched an investigation.
The disclosure comes 11 months after the CDC also mishandled anthrax.
Researchers at a lab designed to handle dangerous pathogens sent what they believed were dead samples of anthrax to another CDC lab – one with fewer safeguards and therefore not authorised to work with live anthrax.
Scores of CDC employees could have been exposed to the live anthrax, but none became ill.
The anthrax bacteria sent out by Dugway Proving Ground was part of efforts “to develop a new diagnostic test to identify biological threats”.
The lethal disease is spread by spores and has been used for bioweapons programmes in the US and elsewhere.
Its microscopic spores can be released without being detected and can be placed in powders or food.
In 2001, powdered anthrax spores were found in letters mailed in the US. Out of 22 people who were infected, five died.
The disease is deadly unless a patient is quickly given large doses of antibiotics.