Worries about the smoke, which can be seen from space, and what's in it, prompted the U.S. Environmental Protection Agency to set up air monitors and bring in a special airplane that checks for radiation levels, ABC News reported Wednesday.
So far officials have found nothing.
"Our facilities and nuclear material are protected and safe," Laboratory Director Charles McMillan told ABC News.
The Los Alamos lab will be closed until at least Thursday because of the proximity of the Las Conchas fire to the facility's grounds, CNN said.
"Laboratory facilities will be closed for all activities and non-essential employees are directed to remain off-site," the lab said in a statement.
The Las Conchas fire broke out Sunday and by early Wednesday had consumed about 61,000 acres. Officials said it was 3 percent contained.
McMillan said hazardous materials were secure and safe at the facility following a small fire that broke out Monday on the grounds and was quickly extinguished.
The Las Conchas fire was skirting the southern border of the lab's 40-square-mile facility and is near the western border, Los Alamos Fire Chief Doug Tucker said.
Voluntary evacuations began Sunday in Los Alamos and White Rock, southeast of Los Alamos, but became mandatory for Los Alamos residents by Tuesday, officials said.
New Mexico Gov. Susana Martinez warned citizens against using fireworks on Independence Day and the rest of the season.
The Las Conchas fire, which started on private land and spread into the Santa Fe National Forest and the Jemez Ranger District, is one of several wildfires in the region, indicated information on InciWeb, which provides the Incident Information System and compiles information from government agencies.
The Pacheco fire was burning Wednesday in the Pecos Wilderness, 2 miles north of the Santa Fe Ski Basin, CNN reported. It has scorched 10,000 acres since it began June 18 and was about 20 percent contained.
The Donaldson and Game fires south of Hondo and U.S. Highway 70 merged into one blaze that has burned about 15,000 acres and was not contained, the New Mexico Fire Information Web site said.
In Arizona, the Wallow fire -- the largest wildfire in the state's history -- was about 89 percent contained Tuesday, the Arizona Emergency Information Network Web site said. Since it began in late May, it has consumed 538,049 acre, of which 15,407 acres are in New Mexico.
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