An investigation into the mistaken shipment of deadly bird flu virus from a government laboratory earlier this year found that a scientist took shortcuts to speed up the work and accidentally contaminated the samples, the Centers for Disease Control and Prevention reported Friday.

As a result, the CDC shipped a virulent avian flu virus rather than a relatively benign animal strain to a poultry research laboratory of the Department of Agriculture. No one became infected or fell ill, and the pathogen was destroyed. But after CDC lab members learned of the safety lapse, they didn’t notify supervisors up the chain of command until more than six seeks weeks later.

The CDC investigation said the primary factors behind the reporting delay were the “lack of sound professional judgment” by individuals aware of the contamination and “insufficient or ambiguous” reporting requirements.

CDC Director Tom Frieden has called the reporting delay the “most distressing” aspect of several recent incidents involving the mishandling of dangerous pathogens at the nation’s labs, including potentially exposing dozens of employees to live anthrax. Last month, several vials of long-forgotten smallpox virus were discovered in a building on the Bethesda campus of the National Institutes of Health.

The internal CDC investigation into the flu lab incident found that the scientist failed to follow best practices and no approved laboratory-specific operating procedures existed for the work being done, the report said. The errors most likely happened because the scientist was growing cell cultures from both virus strains at the same time at the same work station, the report found. There were no written records to document the procedures performed.

“We’re pretty sure the person took short cuts,” said Anne Schuchat, director of CDC’s National Center for Immunization and Respiratory Diseases. “In laboratory work, it’s so important to follow every step, and when you’re working with unusual pathogens, it’s even more important that every single step is followed.”

She added: “This wasn’t a question of someone who was poorly trained. There was substantial experience and knowledge.”

It should have taken the scientist a minimum of 90 minutes to process the specimens, including 30 minutes for decontamination. But the scientist spent only 51 minutes in the lab--based on card key readers showing lab entry and exit times--including time spent to shower and change into street clothes, the report said.

The contamination took place Jan. 17, when the scientist began growing a supply of virulent H5N1 strain and the less-dangerous H9N2 strain. The scientist “acknowledged being rushed to attend a laboratory meeting” due to begin 15 minutes after leaving the lab, the report said. At the time, the influenza division had a heavy work load preparing for an upcoming vaccine meeting of the World Health Organization. The scientist and the team leader are experienced researchers in the CDC’s influenza division, said the report, which did not identify any individuals.

Frieden has said that it’s possible that for scientists who work with deadly organisms “day in and day out for weeks, months and years, you can get a little careless. And that’s something that may have happened.”

Schuchat and other top CDC officials have called the lapses unacceptable. The flu incident involves a lab that works with exotic flu viruses. It has been closed since July 9, when senior CDC leaders were told about the contamination. The CDC’s work on seasonal flu surveillance and vaccines has not been affected and is ongoing, officials said.

The deficiencies described in the report come at a time when the CDC is the spotlight for its role battling the worsening Ebola outbreak in West Africa. The agency has about 30 specialists in the countries hardest hit--Sierra Leone, Liberia, Guinea and Nigeria. Another 50 specialists are expected to arrive by the end of August. In the United States, the CDC has the only lab capable of performing diagnostic tests for suspected cases of Ebola.

“We understand how high the stakes are,” Schuchat said. Agency officials have put in place a series of measures in response to the safety lapses, including a moratorium on any biological material leaving CDC’s numerous labs. The moratorium applies to each lab procedure involving biological materials, and is being lifted after procedures meet new safety protocols, officials said.

The agency is also testing all preparations done by the flu lab scientist dating from a year ago; it is also testing preparations sent by the influenza division to other labs over the last year. All influenza labs must now have daily record-keeping.

Staff must also undergo training to understand when events must be reported. Researchers did not report the bird flu contamination initially because they didn’t think the incident qualified as a release of a “select agent,” a designation reserved for the most dangerous pathogens.

The report disclosed that another lab at CDC had also received contaminated flu samples. That team noticed that its experiments were producing atypical results, and asked the flu lab to doublecheck the cell culture.

Paul Keim, a well known pathogen expert at Northern Arizona University, said CDC’s findings suggest that either the lab workers tried covering up the original mistake by not reporting it sooner or that they simply lacked proper training to realize that the incident required immediate reporting.

“Neither of these two things is good,” he said.

Keim said he suspects part of the problem is that most of the work that flu researchers traditionally have done do not involve “select agents.” The apparent lack of familiarity with the strict rules surrounding select agents in the CDC lab could be a sign of deeper problems, he said.

“If their training isn’t up to speed on this, then it isn’t up to speed on other things, and that could lead to accidents,” said Keim. The good news, he said, is that more rigorous training about the existing rules and expectations could help solve the underlying problem.

The investigations were prompted by a June incident 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. During the anthrax investigation, agency officials learned about the bird flu incident and three other instances where deadly pathogens had been improperly sent to other laboratories over the past decade.

A special unit of the USDA is also investigating the incidents; its report has not been made public, a CDC spokesman said.

As a result of the flu lab and anthrax episodes, a “range of personnel actions are in progress,” Schuchat said. The actions include, but are not limited to: suspension, reassignment, written reprimand and counseling, she said. She declined to say whether anyone has been fired.

“The key point is that the agency is holding individuals accountable,” she said, and focusing on fostering a culture of safety so that people will be open about reporting safety deficiencies.

Michael Osterholm, a bioterrorism expert and director of the Center for Infectious Disease Research and Policy at the University of Minnesota, said the CDC’s investigation was thorough and their conclusions solid.

But the report underscores the need for a stronger safety structure.

“What you don’t want to do is allow compounded errors,” he said. “That’s the history of catastrophic events. It’s never just the one error that does it.”