A scientist with the US Centers for Disease Control and Prevention declined to tell superiors that a worker had mixed a lethal strain of bird flu with a more benign one, even though that mixed strain was shipped out to another laboratory.

According an internal investigation into the matter, the dangerous bird flu cocktail was then administered to chickens as part of a US Department of Agriculture (USDA), in which all of the chickens ended up dying. As a result, USDA officials took another look at the bird flu samples in May and notified the CDC that a deadly strain of the virus was detected inside.

No people fell ill due to the bird flu strain, the Associated Press reported, but it apparently remained in circulation for months – it was originally concocted in January – before scientists picked up on what was wrong.

After the CDC confirmed the USDA’s findings, the team member in charge chose not to notify those higher in the chain of command, reportedly because “the viral mix was at all times contained in specialized laboratories and was never a threat to the public.”

However, when another lab reported similar problems – a Maryland facility reported that more than 300 vials containing influenza, dengue, and other pathogens were discovered in an unused storage room – the team leader brought the dangerous bird flu strain to the attention of more senior officials.

Although it’s unclear exactly how the bird flu strain was created, the report did clarify a couple of things. The lethal strain was supposed to be handled separately from the less dangerous one, and the entire process should take at least 90 minutes. The scientist involved, however, completed his work in only 51 minutes in order to rush to a meeting, meaning that it’s very likely “shortcuts” were taken. The CDC told the AP “it’s possible the scientist worked on both strains at the same time.”

This revelation comes in the wake of previous reports about lax safety at CDC laboratories. As RT reported in June, about 84 scientists were potentially exposed to anthrax after employees failed to properly sterilize the deadly bacteria. Although no one became sick and no reports of exposure have been filed, the eye-opening incident sparked an investigation that revealed multiple failures in safety protocol.

“These events revealed totally unacceptable behavior,” CDC Director Tom Frieden said at the time. “They should never have happened. I’m upset, I’m angry, I’ve lost sleep over this, and I’m working on it until the issue is resolved.”

Both the flu lab and the anthrax lab have been closed, and the anthrax lab director has since resigned.

Another investigation, meanwhile, found that dangerous microbes and “unidentified materials” were transported between labs in plastic Ziploc bags – containers which fail to meet the CDC’s “durability” requirement. In some cases, anthrax samples were found to be missing and had to be tracked down, while others were placed in unlocked labs not authorized to store the deadly bacteria.

“An internal investigation found serious safety lapses, including use of an unapproved sterilization technique and use of a potent type of anthrax in an experiment that did not require a live form of the germ,” the Associated Press reported in July.