Officials at one of the nation’s premier nuclear labs are investigating the potential exposure of employees to plutonium.

Los Alamos National Laboratory confirmed Monday that 15 workers were being evaluated after a breach involving a gloved box that was being used to handle the material. The incident happened in June.

The area inside the plutonium facility was secured and there was no risk to public health or safety, lab officials said in a statement sent to The Associated Press.

“Laboratory employees responded promptly and appropriately and cleared the room in a safe manner,” the lab said.

It’s unknown how long the review will take and what changes might be made to ensure another breach does not happen.

Los Alamos is preparing to resume and ramp up production of the plutonium cores used to trigger nuclear weapons. It’s facing of a 2026 deadline to begin producing at least 30 cores a year — a mission that has the support of the most senior Democratic members of New Mexico’s congressional delegation as the work is expected to bring jobs and billions of federal dollars to update buildings or construct new factories.

The effort has drawn much criticism from nuclear watchdog groups that long have been concerned about the lab’s safety record and missed deadlines and repeated cost overruns.

State officials also have voiced concerns about the federal government’s ability to clean up existing contamination from decades of bomb making and nuclear research at the lab while generating new waste.

To meet a mandate set by the federal government to replace the nuclear stockpile’s aging plutonium cores, the work is being shared by Los Alamos and the Savannah River Site in South Carolina. Congress is hashing out how much money will be funneled to the two sites as part of ongoing negotiations on the latest defense budget bill.

Los Alamos began as a secret city in the mountains of northern New Mexico where government scientists and the military gathered as part of the Manhattan Project to develop the first atomic bomb. Since the 1940s, it has grown into a massive complex.

The mission of producing the plutonium cores has been based at Los Alamos for years but none have been manufactured since 2011 as the lab was dogged by a string of safety lapses.

The June 8 incident at the lab’s plutonium facility was recently made public in a weekly report by inspectors with an independent safety board that monitors activities at federal labs around the country.

According to the report, air monitors sounded when an employee pulled out of the glovebox gloves after weighing and packaging plutonium oxide powder. Significant contamination was noted on his protective clothing, hair and skin. Nasal swabs were positive, and airborne radioactivity was documented in the room.

The inspector reported that radiation protection personnel successfully decontaminated the worker and that 14 other workers also were being monitored.

(AP)