A massive wildfire that has burned more than 265 square miles in the Gila National Forest has become the largest fire in New Mexico history, fire officials confirmed Wednesday.

The erratic blaze grew overnight to more than 170,000 acres, surpassing a blaze last year that burned 156,593 acres in Los Conchas and threatened the Los Alamos National Laboratory, the nation’s premier nuclear facility.

The Gila forest fire is also the largest currently burning in the country. It formed last week when two lightning-sparked blazes merged in an isolated mountainous area in southwestern New Mexico, where it has destroyed about a dozen homes and prompted evacuations of nearby towns and health alerts for some of the state’s largest cities.