Workers at the U.S. national nuclear laboratory in Los Alamos, New Mexico, have been conducting controlled burns and mowing excess brush to fend off a raging wildfire threatening the area.
Officials said the lab will be closed until Friday. The lab and residents of Los Alamos were evacuated on Monday.
Lab officials have said all nuclear and hazardous material - including hazardous waste stored on the complex - is safe. Radiation tests conducted by plane have revealed no contamination to the air.
Federal fire officials say the Las Conchas blaze near Los Alamos is the biggest of a half-dozen wildfires active in the drought-ridden state of New Mexico. The fire has covered more than 28,000 hectares and is considered only 3 percent contained.
Wildfires are also burning in the neighboring state of Arizona, where the Wallow fire has burned more than 200,000 hectares but is now considered 95 percent contained.
Officials say large fires are burning in nine U.S. states, including the southern states of Texas, Georgia, and Florida.
Some information for this report was provided by AP, AFP and Reuters.