Officials from the Los Alamos National Laboratory say dangerous materials are safely stored.
Hundreds more firefighters are being deployed to battle a wildfire near a top US nuclear weapons research lab in New Mexico amid concerns the blaze could reach radioactive waste.
Nearby residents have expressed concern about potential contamination if flames reach barrels stored outside.
But officials are confident the blaze will not reach the drums and they say dangerous materials are safely stored.
The town outside Los Alamos National Laboratory was evacuated on Monday.
On Wednesday, there were expected to be between 600 to 800 firefighters tackling the blaze, deputy incident commander Mike Bradley told the Albuquerque Journal, adding that the number could climb as high as 1,000.
Air National Guard members from Colorado, California and North Carolina have also flown in to help local crews battle the blaze near the lab, which remains closed to all but essential staff until at least Thursday.
The Environmental Protection Agency has deployed air monitors and aircraft that can monitor radiation levels, amid fears the blaze could reach a cache of 30,000 drums, each containing 55 gallons (208 litres) of plutonium-contaminated waste.
http://www.bbc.co.uk/news/world-us-canada-13963361
Note: Update Record,29 June 2011 Last updated at 15:54 GMT