The head of the lab that potentially exposed scores of employees of the Centers for Disease Control and Prevention in Atlanta to anthrax resigned abruptly this week, the agency confirmed Wednesday.

Michael Farrell had been the team leader for the CDC’s Bioterrorism Rapid Response and Advanced Technology laboratory since 2009. But he was reassigned last month after workers inadvertently sent live anthrax samples to researchers in other CDC labs.

Farrell submitted his resignation on Tuesday, said CDC spokesman Tom Skinner, who declined to offer further details about Farrell’s departure, including whether agency officials had asked him to resign. He also said Farrell had declined all interview requests.

The potential exposures in Farrell’s lab took place after a scientist failed to follow adequate protection procedures to inactivate anthrax samples being sent from the bioterrorism lab in Atlanta to several other CDC labs. Workers at the other labs, believing the samples had been inactivated, were not wearing adequate personal protective equipment while handling the material.

The unintentional exposure was discovered June 13 when the original bacterial samples were gathered for disposal and found to contain live bacteria. The CDC has said that more than 80 employees might have been exposed to the deadly toxin, though no illnesses have been reported.

In the wake of the anthrax scare, the CDC earlier this month disclosed that it was only the latest security lapse at the agency. In a string of incidents in recent years, the agency said, CDC researchers have mistakenly shipped out other dangerous pathogens, including botulism bacteria and samples of the virulent H5N1 influenza virus.

“These events should never have happened,” CDC Director Tom Frieden said, even as he noted that no one had been sickened or harmed. “I’m disappointed, and frankly I’m angry about it.”

In addition, audits by government inspectors and inquiries by the Government Accountability Office have documented numerous other safety lapses at the CDC and other labs that handle deadly pathogens over the past decade, from inadequate building security to unlocked freezers to poor inventory records.

Top CDC officials have not singled out Farrell for blame, at least publicly, in the failures that led to the recent anthrax incident. During a hearing last week on Capitol Hill, Frieden told lawmakers that more troubling than any one blunder was the fact that the agency had failed to address systemic safety issues at government labs over the years.

We missed a critical pattern,” Frieden said. “And the pattern is an insufficient culture of safety.”

Farrell had been reassigned following the June incident, and his future at the CDC was uncertain before his resignation this week. Sean Kaufman, a biosafety expert who also testified at last week’s congressional hearing on lab issues at the CDC, said Farrell had unfairly been made a scapegoat.

“Michael immediately reported this incident. He did what he needed to do as a scientist. And when he did that, the repercussion was a loss of a job,” said Kaufman, a former CDC employee who conducted a training in Farrell’s lab as recently as this spring. “This is nothing but pointing a finger and holding a scientist responsible for something that’s a systemic issue within an organization.”

Kaufman said the hasty departure of Farrell, whom he described as a meticulous scientist, father of two boys and Navy veteran, could discourage other employees from reporting future lab incidents and ultimately undermine safety.

“There are people now who are more afraid to step forward and report accidents than they were before,” he said. “Who wants to step forward now and say, ‘Hey, I made a mistake’ ?”

Frieden has vowed to take “sweeping measures” to improve the culture of safety at the CDC, which conducts some of the world’s most sophisticated research into infectious diseases. As part of that effort, he has established a high-level working group to review and approve safety on a lab-by-lab basis. He also appointed an agency veteran, Michael Bell, to oversee lab safety.