AIKEN — Federal authorities are investigating a security breach that compromised personal information of thousands of workers at the Savannah River Site near Aiken.

The U.S. Department of Energy says no classified data was part of the information accessed. Officials say the data disclosure involved information from at least 12,000 workers at Savannah River.

The department’s Office of Inspector General is investigating.

The 310-square-mile Savannah River Site once produced plutonium and tritium for atomic bombs. Work there is now focused mostly on research and cleaning up contaminated areas.