A fire at the Savannah River National Laboratory, part of the expansive Savannah River Site in South Carolina, prompted an emergency response Wednesday and raised concerns about the possibility of radioactive contamination spreading beyond the facility.

The site plays a significant role in maintaining the U.S. nuclear arsenal. Its work includes processing tritium for warheads and handling other components used in nuclear weapons.

Officials declared an emergency at  site and employees were evacuated and moved to shelters as a precaution, while air, rail and river traffic in the area was restricted. Earlier in the day, officials had urged nearby residents to monitor local news for instructions about any steps they might need to take.

The emergency was lifted after few hours, after firefighting operations had concluded. Officials said one person suffered minor injuries and that monitoring detected no radioactive contaminants outside the facility. The cause of the fire has not yet been determined.

The Savannah River Site is operated by two private contractors. Battelle Savannah River Alliance manages the laboratory, while Savannah River Nuclear Solutions, LLC, manages the defense site.