Federal government laboratories in Atlanta improperly sent potentially deadly pathogens, including anthrax, botulism bacteria and a virulent bird flu virus, to other laboratories in five separate incidents over the past decade, officials said Friday.

The incidents, which raise troubling questions about the government’s ability to safely store and transport dangerous microbes, prompted the Centers for Disease Control and Prevention to halt operations at its bioterrorism rapid-response lab and an influenza lab and impose a moratorium on any biological material leaving numerous other CDC labs.

“These events should never have happened,” CDC Director Thomas Frieden said Friday in a conference call with reporters. The American people “may be wondering whether we’re doing what we need to do to keep them safe and to keep our workers safe,” he said. “I’m disappointed, and frankly I’m angry about it.”

No one became infected or fell ill in those incidents, and all the organisms were safely disposed of, Frieden said.

The CDC disclosed the incidents in a report Friday detailing safety lapses that occurred last month, when as many as 84 workers may have been exposed to live anthrax after employees unknowingly sent samples of the bacterium from one CDC lab to other CDC labs.

As part of that internal investigation, the agency found that “this is not the first time an event of this nature has occurred,” the report said. “At the time of this writing, CDC is aware of four other such incidents in the past decade.”

Frieden found out about one of the incidents only on Wednesday. A sample of flu virus contaminated with the deadly H5N1 influenza virus was inappropriately sent in March from a CDC lab in Atlanta to a U.S. Department of Agriculture laboratory in Athens, Ga. CDC staff members became aware of the contamination about six weeks ago but apparently never reported it to agency leaders. “I learned about it less than 48 hours ago,” Frieden said, calling it “an unacceptable delay.”

Frieden said he has established a high-level working group to review and approve safety on a lab-by-lab basis. He also appointed a top official to be the single point of accountability. CDC operates some of the world’s most advanced and most secure laboratories for handling infectious germs.

Michael T. Osterholm, a bioterrorism expert and director of the Center for Infectious Disease Research and Policy at the University of Minnesota, said all the mishaps are troubling, but he singled out the one involving H5N1, the much-feared bird flu strain that has infected 650 people worldwide since 2003, killing more than half of them.

“Somehow, you had this potentially lethal virus cross-contaminating what should have been a relatively safe virus,” Osterholm said.“When you can have that type of contamination occur, then have the specimen sent out for others to handle, not knowing what’s in it, that’s a really significant issue.”

The release of the CDC report comes days after government officials discovered decades-old vials of smallpox in a building on the Bethesda campus of the National Institutes of Health. The vials were flown to the CDC on Monday, and Frieden said Friday that two of the six vials labeled as smallpox have shown growth in tissue cultures, meaning the samples are viable, or alive.

It could take as long as two weeks to determine whether the remaining samples also are viable. In the meantime, researchers at CDC will sequence the genetic makeup of the smallpox before destroying the samples in the presence of officials from the World Health Organization.

“That’s what should have been done decades ago, and that’s what will be done now,” Frieden said.

He said the vials included a date — Feb. 10, 1954 — after smallpox had disappeared from the United States but decades before it had been eradicated worldwide.

“Whoever created these vials didn’t do so out of malice,” Frieden said.

It remains unclear how the smallpox samples ended up in a lab that the Food and Drug Administration had operated on the NIH campus since 1972. On July 1, a scientist preparing for the lab’s move to the main FDA campus in White Oak, Md., found the smallpox samples in a third-floor cold-storage room kept at about 40 degrees Fahrenheit.

There is no cure for smallpox, which killed hundreds of millions of people in the 20th century alone before being eradicated in the late 1970s. Historically, about one-third of people who contracted the disease died.

This was the first time the deadly virus has been discovered outside the only two facilities in the world where smallpox samples are allowed to be stored — a highly secure lab at the CDC in Atlanta and a virology and biotechnology research center in Novosibirsk, Russia.

NIH Director Francis S. Collins told employees in an e-mail Friday that investigators will examine “all freezers, refrigerators, cold rooms, storage shelves, and cabinets, as well as all other areas of storage such as offices associated with laboratories” as part of a “clean sweep” to account for materials inside the government’s research facilities.

House Republicans have scheduled a hearing next week on the anthrax incident.

“The repeated breakdown in protocols and safety failures involving the world’s deadliest germs and pathogens is wholly unacceptable,” Rep. Fred Upton (R-Mich.), who chairs the House Energy and Commerce Committee, said in a statement.

The CDC report said that last month’s anthrax incident in Atlanta happened because scientists were using unapproved and inappropriate processes to inactivate anthrax bacteria when transferring samples from a CDC bioterror lab to other CDC labs not equipped to handle live anthrax.

In the bird flu incident, CDC had intended to send a less-dangerous flu strain to the USDA’s Southeast Poultry Research Laboratory. Somehow, that strain became contaminated with the deadly bird flu strain at CDC’s highly regarded influenza lab. USDA lab workers noticed that the sample was “not behaving” like the less dangerous flu strain, Frieden said. The lab found the contamination and notified CDC staff members on May 23. However, Frieden said he and other top officials did not learn of the incident until Wednesday.

Besides the anthrax and bird flu incidents, the CDC report described three other events involving improper pathogen handling:

● In 2006, a CDC bioterror lab transferred vials of anthrax DNA to two outside laboratories, the report said. The bioterror lab “believed they had inactivated the samples,” but testing found viable anthrax bacteria. The bioterror lab instituted new procedures for shipping or transferring DNA from bacterial agents. That same lab was involved in last month’s anthrax incident; workers did not follow those safety procedures, the report said.

● In 2006, shipments from another CDC lab were found to contain live botulism bacteria, which can cause paralysis in infected people. The bacterium produces a nerve toxin in the body. There are five main types, including food-borne. All forms can be fatal. Botulism causes muscle weakness and kills by paralyzing the respiratory muscles.

● In 2009, newly available test methods show that a strain of Brucella, which can cause a highly contagious bacterial infection called brucellosis, had been shipped to outside laboratories as early as 2001 because researchers believed mistakenly that it was a vaccine strain of the bacteria.