A large wildfire moving across northern New Mexico Tuesday had authorities watching for a potential release of radiation around the nation's main nuclear-weapons lab in Los Alamos.

The fire, covering some 60,740 acres, was headed north toward the Los Alamos National Laboratory, the nuclear-research facility that sprawls across 36 square miles and contains 2,000 buildings. The complex, where scientists working on the Manhattan Project developed the atomic bomb in World War...