Law enforcement officials determined Monday that there was no explosive residue on a delivery truck that triggered an emergency response at a former bomb-making site that still handles nuclear materials.

The delivery truck had caught the attention of a bomb-sniffing dog at the Savannah River Site, and initial electronic tests also indicated the possibility of explosive residue, officials said in a news release. Law enforcement from South Carolina and Georgia was called in to help on-site security guards, and site barricades went up to keep out incoming traffic.

About two hours after the site issued its first security alert to the public, investigators announced that they found no explosive residue or devices on the truck.

The site near the Georgia state line that's owned by the Department of Energy returned to normal activity after the all-clear was given shortly before 6 p.m.

The Savannah River Site was built in the 1950s to produce plutonium and tritium for atomic bombs. The site has also produced plutonium for NASA to use in space exploration and uranium for electricity production.

Current work at the 310-square-mile site ranges from cleaning up areas contaminated by weapons production to storing and processing nuclear material.