Washington: US authorities investigating the mistaken shipment of live anthrax by a military lab have discovered another batch of the lethal bacteria dating back to 2008, some of which was sent to Australia.

Officials said the investigation turned up another batch of live anthrax, which was meant to be made inactive or "dead" in 2008.

US authorities have discovered part of a batch of anthrax was sent to Australia in 2008.

It was not clear precisely when samples from the 2008 batch 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," said a US official who spoke on condition of anonymity.