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(WJW) – The Centers for Disease Control and Prevention says recent lab testing didn’t find any signs of smallpox in the vials found in a Merck facility outside of Philadelphia.

According to the CDC, the U.S. government was notified on Monday about a small number of intact, frozen vials labeled “smallpox” found in the lab by a worker who was cleaning out the freezer.

After testing, the CDC confirmed that the vials contain vaccinia, which is the virus used in smallpox vaccine. There’s no evidence of variola virus, which causes smallpox.

No one was exposed to the contents of the vials.

According to Yahoo News, variola virus is so deadly that only two labs worldwide are authorized to store samples of it. One is in Russia and the other is at a CDC site in Atlanta.