FILE: A member of the  Utah National Guard participates in a training scenario Nov. 4, 2014, at U.S. Army Dugway Proving Ground, the facility from which the Defense Department inadvertently shipped live samples of anthrax earlier this year. (Defense Department photo)

A Defense Department review of how an Army laboratory in Utah distributed scores of live anthrax samples to facilities across the United States and overseas found systemic problems with irradiation and testing procedures that have been used there for a decade, but determined that a root cause is still not certain.

The review was called for by Deputy Defense Secretary Robert O. Work in May following the revelation that Dugway Proving Ground in Utah inadvertently shipped live samples of the deadly bacteria that reached at least 86 commercial and government laboratories in seven foreign countries, 20 U.S. states and the District of Columbia.

Work said in a news conference Thursday that he expects that the number of labs involved will continue to grow as the Centers for Disease Control and Prevention track where the anthrax samples were distributed. The review found that 17 of 33 batches grown and irradiated at Dugway and tested again as part of the review were found to contain live anthrax after they were labeled as dead.

[Previous coverage: Organizations sent suspected live anthrax by military lab, including Pentagon agency]

“Obviously, when over half of those anthrax batches that were presumed to be inactivated were then proven to contain live spores, we have a major problem,” Work said. He later added: “We are shocked by these failures.”

Work said he directed Army Secretary John McHugh to conduct an investigation into who was responsible for making decisions that led to the problems. It isn’t clear what form that might take, but Frank Kendall, undersecretary of defense for acquisition, technology and logistics, suggested that the Army inspector general could become involved. He oversaw the review that Work ordered.

McHugh is “deeply troubled by the report’s findings” and has ordered a corrective plan to be developed, Army Col. David P. Doherty, a service spokesman, said in a statement Thursday. An investigation will be launched to determine any failures of leadership, he added.

The first live sample was reported May 22 by a private, undisclosed laboratory in Maryland that received it from the Edgewood Chemical Biological Center at Aberdeen Proving Ground, northeast of Baltimore. The samples were to be used in testing to help develop ways to find live anthrax in the field. The anthrax was supposed to have been killed by gamma radiation.

A 38-page report released by the Pentagon on Thursday said that while Dugway is one of several government facilities that store and irradiate live anthrax, the lab is the primary producer of it and other toxins used in research. It made the largest batches of any Defense Department facility, tested the smallest samples to make sure they were dead and did so the soonest after irradiation was applied.

The review raised the possibility that some anthrax may have been damaged by the gamma rays, but not killed. Given time, the bacteria can regenerate itself, investigators found.

[How anthrax became an unexpected challenge for the Pentagon]

“It is recommended that a series of experiments be performed to ensure that all DoD laboratories working with [anthrax] use conditions that allow for the capture and growth of any injured spore,” the report said.

The review also said it cannot be ruled out that live and irradiated anthrax were cross-contaminated. It recommended testing anthrax after irradiation in a different facility.

Work said Thursday that while he was unhappy with the findings of the review, it was highly unlikely that an employee working with the anthrax could have been infected. Anthrax is highly contagious in powder form, but was shipped as a liquid in several forms of packaging. To get sick, a healthy individual would have needed to drink more than one sample, he said.