After a two-hour lockdown, a nuclear site in South Carolina was reopened after a hyper-vigilant bomb-sniffing dog unintentionally stopped a delivery truck on Monday.

The dog had barked at a truck that delivered vending machines for the Savannah River Site. Law enforcement officials did not find any explosive residue or device when they inspected the truck.

The facility purifies highly enriched uranium and is part of the nuclear alarm of the Department of Energy, according to Reuters.

The site had announced that there had been a "potential security event in progress," and that the barricades of the site were closed to incoming traffic momentarily on their official Facebook page.

Once the site, which is near the Georgia state line, were given the all-clear, normal activities were resumed shortly before 6 p.m.

The Savannah River Site was built in the 1950s to manufacture plutonium and tritium for atomic bombs. It has also manufactured plutonium for the National Aeronautics and Space Administration (NASA) to use for space exploration as well as uranium for electricity production.

Current types of jobs that people do at the site include cleaning areas that had been contaminated by the production of weapons as well as the stowing and handling of nuclear material, according to the Associated Press.