Story highlights The Pentagon expects the number of sites suspected of receiving live anthrax to go up as its investigation continues.

The Pentagon's police force is one of the agencies that received questionable U.S. Army shipments of anthrax.

Washington (CNN) The UK has joined the list of countries that unintentionally received shipments of live anthrax samples from the Pentagon.

However, British authorities said the samples, from 2007, were no longer a threat.

"We do not believe there is any continuing health risk to staff or to the public," the UK's Health and Safety Executive said in a statement, noting that the company at issue -- which is not being named -- has been in touch with the Defense Department about the matter.

South Korea, Australia and Canada have already been named as recipients of questionable anthrax samples, along with 19 states and the District of Columbia.

Deputy Secretary of Defense Robert Work said last week that he expects the numbers of labs suspected of receiving live anthrax to go up as the Pentagon continues its investigation into the shipments, some of them made via FedEx. When put in the mail, the samples were not believed to contain live samples of the disease.

Read More