The worst of it came shortly after 1 a.m. last Thursday when firefighters were hosing down the tindery brush on the western edge of the Los Alamos National Laboratory. The wind was gusting to 60 miles an hour, and suddenly they were fighting two fires at once--the brush fire at ground level and a "crown fire" high overhead, a contagion of flame that leapt from tree to tree, threatening to outflank them. "I've fought brush fires and forest fires and urban fires," one exhausted fireman told NEWSWEEK. "But I've never seen it like this."

Driven by relentless winds that blew for more than a week, the fire burned upwards of 36,000 acres, displaced 25,000 people and destroyed 261 homes in Los Alamos, N.M., home of the top-secret government lab that built the first atomic bomb in 1945 and still designs U.S. nuclear weapons. Last week the Los Alamos area was blanketed with acrid smoke coming from the Cerro Grande fire, named for a nearby peak where it began on May 4. The irony was that the blaze was deliberately set by the U.S. Park Service to reduce fire risk to the lab--a decision that outraged residents and forced the suspension of Roy Weaver, the Park Service official who approved what was supposed to have been a "prescribed burn."

The threat was that the flames would reach stockpiles of plutonium and other weapons materials stored on the Los Alamos reservation. That could create a cloud of radioactive smoke--an environmental catastrophe and a powerful health risk to anyone downwind. …