By Julie Steenhuysen and Sharon Begley

(Reuters) - Federal health officials on Friday disclosed a new safety breach at a high-security U.S. government laboratory involving dangerous avian flu, a lapse that came to light as they investigated the potential exposure of researchers to live anthrax bacteria.

The U.S. Centers for Disease Control and Prevention said an internal probe found multiple failures by individual scientists and a lack of agency-wide safety policies led to the potential exposure of more than 80 lab workers to live anthrax at its Atlanta campus last month. Researchers in a high-security bioterror lab sent samples of what they thought were inactivated bacteria to colleagues in a lower-security lab, with fewer protections.

Investigators also discovered a previously unreported incident: Workers at a separate high-security CDC influenza lab sent samples containing a dangerous strain of bird flu to counterparts at the U.S. Department of Agriculture in March. Mishandling avian flu could have far graver consequences than anthrax does, though no one has been found to have been infected in either case.

The two incidents represent the latest in a series of breaches at the CDC in the last decade that are drawing fresh scrutiny from Congress, including questions about the agency's ability to oversee potentially dangerous research. The CDC said its findings provide a "wake-up call" to overhaul the standards governing experiments with deadly pathogens nationwide.

Biosecurity has focused on "how to keep bad guys out of the lab," Michael Osterholm of the University of Minnesota and a member of the National Science Advisory Board for Biosecurity, which advises the federal government, said in a telephone interview. "One of the critical issues we need to focus on is the good guys who just forget to do it safely."

The CDC's director, Dr. Thomas Frieden, called the bird flu incident “the most distressing,” in part because it occurred six weeks ago but was not reported to senior agency leadership.

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"I learned about it less than 48 hours ago," he told reporters in a teleconference, adding that the events likely "have people questioning government."

"We need to look at our culture of safety throughout all of our laboratories," Frieden said. "I’m upset, I'm angry. I've lost sleep over it and I'm doing everything I can to make sure it doesn't happen again."

Frieden also pointed to the discovery this month of six vials of smallpox in an unused room at the National Institutes of Health campus in Bethesda, Maryland, near Washington. Frieden disclosed on Friday that two of the vials dated from 1954 contained live smallpox virus, a global scourge for centuries.

The CDC's anthrax report does not name any of the responsible individuals. Frieden said the CDC would discipline any staff who knowingly violated research procedures or failed to report a lab breach.

"These repeated safety failures raise grave concerns about the CDC’s ability to ensure strict procedures, protocols and training are followed," said Representative Tim Murphy, chairman of a House Energy and Commerce subcommittee that has called Frieden to testify on Wednesday.

The Senate Health, Education, Labor and Pensions Committee is also pressing U.S. Department of Health and Human Services, which oversees the CDC, for answers, according to a letter to HHS Secretary Sylvia Burwell.

An HHS spokesman said the CDC has outlined "corrective actions" to prevent future mishaps at its laboratories.

"Dr. Frieden is leading those efforts," the spokesman said.

The CDC is suspending any transfers inside or outside the agency of biological materials, including infectious agents and even inactivated specimens, from high-biosecurity labs. Both the CDC bioterror lab that handled the anthrax bacteria and the agency's influenza lab are closed pending further study of what happened.

BIRD FLU CONCERNS

Outside experts agreed that shipping what CDC scientists believed were samples of a fairly benign form of influenza but which were mixed with the highly pathogenic H5N1 bird flu was even more alarming than the anthrax incident.

"The last place you want to be mixing up samples is in influenza," said Osterholm. "The ability for that to jump from the lab bench to the community is substantially greater."

H5N1, although highly lethal, is not easily transmitted from one infected person to another, which would limit its spread in case of a lab-acquired infection or an escape from a lab.

Other scientists raised alarm over the CDC disclosure that the same lab responsible for the anthrax incident had a similar lapse in 2006, when researchers transferred what they thought was inactivated bacteria to another facility.

"That the same kind of incident can recur shows that the CDC does not learn from its own mistakes," molecular biologist Richard Ebright of Rutgers University and an expert on biosafety said in a telephone interview.

Just a year earlier, the CDC published recommendations on how to prevent shipments of what scientists believe to be inactivated anthrax but which are in fact viable.

THE ANTHRAX PROBE

In the anthrax case, investigators found that the scientists failed to follow an approved study plan that met safety requirements and lacked standard procedures to document when microbes are properly inactivated. The researchers were not aware of the most recent scientific literature on how best to inactivate the bacteria.

Once CDC officials were alerted to the breach, their response also fell short. For instance, CDC scientists in other labs first learned of the event not through official communication but "by witnessing CDC closing and/or decontaminating laboratories," the report said.

Other deficiencies noted in the report included inconsistent decontamination procedures in the affected labs and a lack of clear command for handling the incident in the first week after it occurred.

To prevent future mishaps, CDC is creating a "lead laboratory science" position to be accountable for safety and setting up an external advisory committee on biosafety.

Rutgers' Ebright suggested that an outside agency should oversee CDC's work with dangerous pathogens.

"Without removing the responsibility for oversight from the very organization that carries out the work, it's hard to think that the recommendations will really be implemented," he said.

(Reporting by Sharon Begley in New York and Julie Steenhuysen in Chicago; Additional reporting by David Morgan in Washington; Editing by Michele Gershberg, Jonathan Oatis and Dan Grebler)