Four radioactive wasp nests have been discovered at a South Carolina nuclear facility, according to federal officials.

The first nest, which was found by workers at the Savannah River Site early last month, was recently disclosed in a report from the Department of Energy, which owns the site. The facility, near Aiken, S.C., produced material for nuclear weapons throughout the Cold War.

Three additional nests have since been discovered at the site, officials told The Times on Friday.

“The U.S. Department of Energy is managing the discovery of four wasp nests with very low levels of radioactive contamination,” Edwin Deshong, the manager of the department’s Savannah River Operations Office, said in an emailed statement. “The nests do not pose a health risk to SRS workers, the community, or the environment.”

But the discovery raised questions about the extent of the environmental contamination at the site, said Timothy Mousseau, a biologist at the University of South Carolina who studies organisms and ecosystems in radioactive regions of the world, including Chernobyl, Ukraine, and Fukushima, Japan.

“This is an indicator that there are contaminants spread across this area that have not been completely encased and protected,” Dr. Mousseau said.

The discovery of additional radioactive nests, he added, “indicate that much greater effort must be made to assess the possible risks and hazards of what appears to be a significant source of radioactive pollutants.”