Government scientists Thursday determined that vials marked “smallpox” found in a Montgomery County lab did not actually contain the virus that causes the deadly illness.

In a statement, the Centers for Disease Control and Prevention said frozen vials labeled “smallpox” that were discovered by a lab worker in a Montgomery County vaccine research center contained vaccinia, the virus used in the smallpox vaccine. There did not appear to be any traces of variola virus, the virus that causes smallpox, the CDC said.

“There is no evidence that the vials contain variola virus, the cause of smallpox,” the CDC said in the statement.

The agencywas first notified of a report of the intact, frozen vials Monday, the CDC said. The lab worker had found the vials while cleaning out a freezer in the research facility. Nobody was exposed to the virus, the CDC said.

There were initial reports that the vials had been found Tuesday night in a Merck facility outside Philadelphia. There are three Merck facilities near Philadelphia — in North Wales, Lansdale, and West Point, according to Merck’s website.

Neither Merck nor the CDC confirmed exactly where the vials were found.

Smallpox, caused by the variola virus, is a highly contagious and deadly disease that was eradicated by 1980 due to an aggressive and global immunization campaign, according to the Mayo Clinic. Symptoms of smallpox include fever, a progressive skin rash, and, in many cases, death, according to the CDC.

Many of those who survived smallpox hadpermanent scars on their body and some were left blind, according to the agency.

By 1980, smallpox was eliminated through vaccines that were widely distributed.

On Wednesday, a professor of chemistry and chemical biology at Rutgers University said that even if the vials had contained smallpox, there was little to no risk of exposure or infection to the lab worker and to the public.