A fire at a national laboratory in South Carolina, located within a former nuclear weapons production complex, prompted an emergency declaration Wednesday, restricting incoming traffic and disrupting air and rail services in the surrounding area.

The fire at the Savannah River National Laboratory, located within the US Department of Energy's Savannah River Site, was extinguished by Wednesday night. Operations at the site subsequently returned to normal, with no detectable contamination reported, according to a statement from the Savannah River Site.

The sprawling complex was once used by the federal government to produce materials for nuclear weapons, primarily tritium and plutonium-239. The laboratory is situated in the northwestern part of the site, near its boundary.

Opened in the early 1950s during the Cold War, the facility now focuses on environmental protection, cleanup, nuclear waste management and the handling of nuclear materials, according to the US Department of Energy.

Edwin Lyman, director of nuclear power safety at the Union of Concerned Scientists, said the laboratory conducts experiments involving nuclear materials and processes radioactive substances. Its activities include recovering radioisotopes from spent nuclear fuel.

Lyman said the reported absence of off-site contamination was reassuring, noting that buffer zones separate most facilities from public areas.

However, he stressed that fires involving radioactive materials require strict safety measures because they can disperse hazardous substances, potentially contaminate surrounding areas and expose members of the public to radiation.

According to the site's community preparedness information, Wednesday's declaration represented the second-highest of three emergency levels, indicating that a relatively serious incident had occurred.

The emergency was lifted Wednesday night after firefighters extinguished the blaze.