The fire has grown to 50,000 acres and destroyed at least 30 structures since it started Sunday.
Towering plumes of smoke could be seen filling the air in Los Alamos. The entire town of 12,000 people has been ordered to evacuate.
A spot fire came within about 50 feet of the perimeter Monday. The flames were extinguished but the danger isn't over.
"We are preparing for the fire to go in any direction. We don't know which way the wind is going to go until it gets here," said Chief Dough Tucker of the Los Alamos Fire Department.
The Los Alamos National Laboratory is a government site that was founded during World War II to develop the world's first nuclear weapons.
Officials say all radioactive and hazardous material is being protected.
A devastating blaze in Los Alamos more than a decade ago destroyed hundreds of homes and buildings.
"A lot of the people I know have already left. They just said they've done this before, so they're getting out early this time," said Los Alamos resident Taylor Guskey.