Decades-old vials containing deadly pathogens, including the plague, were found by U.S. health officials in government laboratories, the latest in a series of hazardous vials that were stored at unsecured labs and forgotten about.

National Institutes of Health officials said Friday they uncovered five containers of "select agents," extremely dangerous pathogens that need to be kept under strict conditions, during searches across its laboratories in Bethesda, Maryland, The Washington Post reported.

In addition to samples of the plague, officials found the muscle-paralyzing disease botulism, a rare tropical infection and the deadly poison ricin, which was found among a collection that dates back to 1914.

The NIH also found a rare bacterium that causes the potentially fatal disease tularemia, also known as rabbit fever, The Post reported.

Alfred Johnson, director of the NIH office of research services, said the NIH has laboratories that are authorized to use select agents and they are regularly accounted for, the Associated Press reported.

But the disease samples were found among historical collections that at one time did not require special handling.

All of the samples "were stored in locations where they should not have been stored," Johnson said according to The Post.

"All of these were found in containers that were intact, and there have been no exposures. It reminds us, just like my garage at home, that from time to time, we need to check."

No employees were exposed and the vials have been destroyed.

The discoveries were made during what Johnson called a "clean sweep," of government laboratories following the July discovery of smallpox vials inside an FDA-run lab at the Bethesda campus. The vials, dating back to the '50s, were found in an unsecured place used for storage.

"NIH takes this matter very seriously," reads an agency memo to employees about the recent finds, according to the AP. "The finding of these agents highlights the need for constant vigilance in monitoring laboratory materials in compliance with federal regulations on biosafety."