Los Alamos National Laboratory (LANL) appears to have escaped unscathed after a large wildfire threatened it yesterday. At one point the blaze triggered a small "spot fire" within the lab's boundaries, which has since been controlled by emergency services.

The Las Conchas fire began on Sunday afternoon in the Jemez Mountains approximately 19 km south-west of the boundary of the lab in New Mexico. By Sunday evening, as the fire began to spread, LANL announced that all facilities would be closed on Monday, and non-essential employees were directed to remain off-site.

Late on Sunday evening, the fire was reported to be less than 1.6 km from the lab's south-western boundaries, as LANL emergency crews teamed up with Los Alamos County and federal fire crews to tackle the blaze. "I'm asking all our employees to stay clear of the lab so the fire crews can do their jobs," said lab director Charles McMillan on Sunday night. "And please keep those crews in your thoughts tonight."

The situation appeared to be escalating by mid-afternoon on Monday as a one-acre spot fire had been identified within a technical area on the lab's south-western boundary. Reports from the field said that the fire had jumped north across New Mexico Route 4 and Los Alamos County conducted a forced evacuation of the town site. LANL emergency officials announced that the lab would remain closed today (Tuesday) as they continued to fight the fire.

'No facilities face immediate threat'

But by 16:45 local time (23:45 GMT) officials were able to breathe a heavy sigh of relief as they announced that the spot fire was under control after air crews had dumped water at the site. "About one acre burned and the lab has detected no off-site releases of contamination," read the update from the LANL Emergency Operations Center. "No other fires are currently burning on lab property, no facilities face immediate threat, and all nuclear and hazardous materials are accounted for and protected."

There had been fears because the area under threat in this latest fire – Technical Area 49 – had been the site of underground hydronuclear experiments in the early 1960s. But subsequent testing has revealed that no contamination exists today at points of public access.

The lab's latest update at 22:00 stated that important lessons had been learned from the Cerro Grande fire of 2000, which caused damage to lab buildings and employees' homes. "Our efforts in recent years to thin ground fuels around the laboratory, coupled with the reduction in fuels caused by historic fires in the area, are helping protect the Laboratory and townsite," said McMillan.

Having been established in 1943 to develop the first nuclear weapons, LANL now has more than 2000 individual facilities covering a wide variety of research including energy and environment. The 93 square kilometre site, owned by the US Department of Energy, has nearly 12,000 employees and its operating costs for 2010 were $2bn.