IDAHO NATIONAL LAB -- The fire chief for Idaho National Laboratory has declared the 109,000-acre Jefferson fire completely contained. Fire Chief Eric Gosswiller declared the fire contained Monday at 6 p.m.

The fire started Tuesday, July 13, not far from the Materials and Fuels Complex (MFC). Winds gusting at more than 50 mph pushed the fire northeast. It eventually burned about 109,000-acres, or 170 square miles.

July 15, the fire was called contained, which means a fire line was built around the perimeter of the fire. At its peak, 300 firefighters were working to stop the blaze.

According to the INL, all employees returned to work Monday. All the power has been restored except at two MFC buildings. Officials say employees who work in those two buildings have been assigned elsewhere until the power is restored.

The cause of the fire is still being investigated. INL officials say it may not be known for several weeks, though a preliminary cause indicates it was somehow started by a human.