Idaho National Laboratory Fire Department responded to a fire alarm at the site out near Arco late Wednesday night.
It's now been confirmed that the fire department was called due to the release of a chemical in one of the drums stored on site.
And that it was located in the Idaho Cleanup Project’s Radioactive Waste Management Complex.
The INL fire department responded last night to the Accelerated Retrieval Project, or ARP5 which is run by the contractor Fluor Idaho.
Shelly Norman, from the Joint Information Center, said "A barrel there and it was elevated temperatures and it was breached and it released some materials..."
While it hasn't been confirmed what was in the specific barrel, they handle materials like plutonium-contaminated filters, graphite molds, and sludges containing solvents and depleted uranium.
Due to the hazardous nature of the materials handled in the building, it had measures able to prevent the spread of any contamination.
Norman also said "Everybody still reported for work... There is restricted movement right at that site but everybody else is just going about their day..."
High Efficiency Particulate Air Filters have trapped any possible contamination in the building, so the facility is back up and running, but for the specific ARP5 building, an investigation is under way, and a time frame for reopening is not yet announced.
Norman explains that "the main concern is safety so the first thing that they are going to do is be looking at what happened and make sure that it is safe for everyone to go back to work and because it's such an important part of it i really don't know how long that would be or where they would go next"
The emergency joint information center has a public information line at (208) 526-5042.