The CDC said despite concerns in recent years about the securing of potential bioterrorism agents such as anthrax and the plague, the labs have strict security measures and protocols in place.
"We always take it seriously. We strive for perfection," Joseph Henderson, director of the CDC's Office of Safety, Security and Asset Management, told USA Today.
The newspaper said private and government audits of the CDC labs as recently as 2010 had cited apparent lapses in security that could result in the loss or theft of dangerous agents.
But Henderson said the labs have redundant layers of security and lab safety, and the public was never at risk due to the security questions.