Firefighters battling the145 square-mile blaze near the nuclear lab in Los Alamos, N.M., believe flames won't reach the facility or the evacuated town nearby.

Fire crews have been working in Los Alamos Canyon to keep the fire away from a six-acre radioactive waste dump near the World War II nuclear facility where the Manhattan Project developed the first atomic bomb.

"The threat is pretty limited," said Kevin Smith, the Department of Energy's National Nuclear Security Administration site manager for Los Alamos, which over sees the lab. "Most of the materials have been dug up."

Some firefighters have been setting backfires in a circle around the site and burning out brush, and other fuels appear to be working to keep the main wildfire away.

"For Los Alamos, it's been a great day. Everything is holding," Los Alamos County Fire Chief Doug Tucker said Thursday evening. "I'm very confident after tonight that once they get done with this, this burn out, that the lower end is safe."

The blaze has forced nearly 10,000 people to leave their homes.

Residents of Los Alamos, who fled the town earlier in the week under an evacuation order, wouldn't be allowed back home until Sunday at the earliest, Tucker said.

The fire has burned tens of thousands of acres a day since it started Sunday, becoming among the largest forest fires in New Mexico history. Crews have contained only 3 percent of the fire.