The Centers for Disease Control and Prevention (CDC) says vials containing smallpox were found at a lab in Maryland and destroyed, but there was no risk to patients or the general public.
Earlier this week, a Maryland university student found one of the vials hidden in a lab at the National Institutes of Health. Tests done on the vials indicated they were from an outbreak in the 1920s but did not contain any live or pathogenic viruses.
The CDC also said that samples from the smallpox outbreak were not stored in an appropriate order at the Maryland lab.
Several previous smallpox cases from the 1920s were observed at Johns Hopkins University in Baltimore, according to AP.
The National Institutes of Health said tests will be conducted on the vials and the vials will be destroyed.
Smallpox was declared eradicated in 1979 but isolated cases were reported in Pakistan and India in the early 2000s.
Some scientists believe that remnants of smallpox virus could still be present in a mammal population.
The smallpox virus is considered one of the most fearsome diseases in recorded history. There have been 55 documented smallpox outbreaks worldwide since the disease was declared eradicated, according to the CDC.