LOS ALAMOS, New Mexico (Reuters) - The wildfire raging for six days near the Los Alamos nuclear weapons laboratory reached record proportions on Friday but has ceased to threaten the sprawling government complex or adjacent town in northern New Mexico, officials said.
The so-called Las Conchas Fire, believed sparked by a downed power line, has blackened nearly 104,000 acres -- or 162 square miles -- of thickly wooded slopes of the Jemez Mountains, mostly in the Santa Fe National Forest, since erupting on Sunday.
Now ranked as the largest wild-lands blaze ever in New Mexico, the fire surpasses the previous record set in 2003 by the 94,000-acre Dry Lakes Fire in the Gila National Forest.
"This is the biggest fire in the history of our state, and it's not over yet," U.S. Senator Jeff Bingaman of New Mexico, said at a midday news conference.
By comparison, the largest blaze in Arizona, the Wallow Fire, has blackened well over 500,000 acres since it erupted May 29 of this year. It is still burning.
The latest fire in New Mexico had for several days crept perilously close to and virtually surrounded the Los Alamos National Laboratory, one of the nation's top nuclear arms production facilities.
At one point earlier this week, the fire's edge was reported just 2 miles from a collection of about 20,000 metal drums containing plutonium-contaminated clothing and other waste stored on a corner of the 36-square-mile lab property.
Nuclear watchdog groups and some citizens also had raised concerns about the fire possibly unleashing residual ground contamination left from decades of experimental explosions and waste disposal in the area.
But a firefighting force that has grown to roughly 1,200 personnel has since managed to carve containment lines around 4 percent of the fire's perimeter on its eastern and southern flanks, keeping flames from invading the lab complex.
Those lines continued to hold on Friday as winds fanned the blaze farther to the north and west, away from the laboratory and adjacent town of Los Alamos, home to some 10,000 residents who remain under evacuation orders.
"We feel extremely confident that the situation is well in hand with respect to protecting our facilities, our equipment and the materials that exist on this property," Tom D'Agostino, director of the National Nuclear Security Administration, said after touring the fire zone.
Governor Susana Martinez said air-quality readings from an aircraft flyover and from 36 ground-based monitors in and around the lab and detected "no abnormalities."
While the Los Alamos vicinity appeared largely out of danger for the moment, officials have set no time frame for lifting evacuation orders for the town, due partly to thick smoke lingering over the area.
The lab remained largely closed, but a few employees were brought in to prepare the facility for reopening.
On Thursday, the blaze encroached on an Indian reservation to the north, the Santa Clara Pueblo, burning at least 6,000 acres of tribal land, including a number of sacred sites.
But the leading western edge of the blaze remained about 6 miles from the nearest populated areas of the pueblo on Friday, fire officials said.
About 150 miles to the south, a separate wildfire caused by lightning blazed in and around the Mescalero Apache Reservation. By Friday morning, the Donaldson Complex Fire had burned some 77,000 acres, about a tenth of that on tribal land, with 10 percent containment reported, authorities said.
Writing by Steve Gorman; Editing by Jerry Norton