Several vials labeled “smallpox” were found in a lab in Montgomery County, Pennsylvania.

The vials were discovered in a freezer, at a Merck facility, where vaccine research is conducted. 

The CDC has been involved, issuing a report that no one has been exposed. The FBI is also said to have gotten involved. 

The facility was placed on lockdown by the FBI and CDC at the time of discovery, on Tuesday, Nov. 16. The lockdown has since been lifted.

Later on Thursday, Nov 18, the CDC concluded the vials did not contain the smallpox disease, but the virus used in the smallpox vaccine.

The frozen vials were found by a laboratory worker who was cleaning out the freezer. The worker was protected via gloves and facial covering.

In the discovery, 15 vials were recovered and deemed questionable. Five were labeled “smallpox,” the disease also known as “variola,” while the remaining 10 read “vaccinia.”

Vaccinia is related to the virus known to cause smallpox. Both smallpox and vaccinia are a part of the poxvirus family. 

Medical officials said vials of smallpox were ordered to be disposed of when the disease was reported as eradicated in 1980 following the last known U.S. outbreak in 1947.

“All of the vials of smallpox that were out in virologists' freezers were supposed to be disposed of once the disease was considered eradicated,” said Dr. Thersa Sweet of Drexel University's Department of Public Health.

Since 1972, routine smallpox vaccinations stopped being commonplace. Today, some researchers and military personnel remain vaccinated. 

Smallpox was originally eradicated through a global vaccination effort. Only the CDC in Atlanta and a Russian institution — the country’s version of the CDC — were known to store the smallpox disease prior.

A similar incident occurred in 2014 in Bethesda, Maryland, when employees at the National Institutes of Health found six smallpox vials in an unused storage room. 

The CDC got involved and insured no one was exposed.

The Strategic National Stockpile currently holds enough smallpox vaccines to reportedly inoculate the entire United States population.