The Pentagon’s second-in-command, Deputy Defense Secretary Robert Work, has ordered an investigation into the mishandling of the live anthrax samples sent to facilities in 11 states and abroad, a senior US defense official told Fox News Friday.

"During our initial look into how live anthrax samples were inadvertently shipped to laboratories, the Department identified additional inadvertent live anthrax shipments," Pentagon spokesman Col. Steven Warren said in a statement.

The department said 24 laboratories in 11 states and two foreign countries -- South Korea and Australia -- are believed to have received suspect anthrax samples. The broadening scope of the problem suggests more extensive flaws in procedures used by the Army's Dugway Proving Ground in Utah to ensure that anthrax samples were made fully inert before shipping them to labs

"There is no known risk to the general public and an extremely low risk to lab workers from the Department's inadvertent shipments of inactivated samples containing small numbers of live anthrax to several laboratories," a separate statement said.

"As of now," the statement released Friday evening said, "24 laboratories in 11 states and two foreign countries are believed to have received suspect samples.  We continue to work closely with the Centers for Disease Control and Prevention (CDC), who is leading the ongoing investigation pursuit to its statutory authorities."

CDC spokesman Jason McDonald said four people at labs in Delaware, Texas and Wisconsin were recommended to get antibiotics as a precaution, although they are not sick. About two dozen people were being treated for possible exposure at Osan Air Base in South Korea.

Fox News confirmed that live anthrax samples were also sent to a lab in Australia back in 2008.

The statement said Work expected the probe to produce results within 30 days.

CDC spokeswoman Kristen Nordlund told The Associated Press the agency iss testing to see which anthrax samples were live. The results are coming in slowly, she said, and the first full set of findings isn't expected until next week.

A Wisconsin commercial laboratory confirmed Friday it was among the labs that received live anthrax spores last week. BBI Detection of Madison, which employs fewer than 20 people, remains partially closed. No employees have gotten sick or are in danger, and there is no danger to the public, said Jackie Lustig, a spokeswoman for Massachusetts-based Alere Inc., which owns BBI.

Fox News' Jennifer Griffin and the Associated Press contributed to this report.