A fast-growing brush fire forced residents of northwestern Reno from their homes Saturday night and prompted Nevada Governor Joe Lombardo to declare a state of emergency in Washoe County.

The Hawk Fire ballooned to cover more than 10,500 acres by late Saturday, with no containment reported, according to state fire officials. Its cause remains undetermined.

“This is an active and rapidly evolving situation, and I urge everyone in the affected areas to remain vigilant,” Lombardo wrote on X. He urged those who were asked to evacuate to do so immediately.

Reno Mayor Hillary Schieve said “structures have already been burned in this fire and your life is more important than a building,” in a message posted by the City of Reno on X.

The fire could be seen rapidly advancing on a downwards slope toward illuminated neighborhoods of Reno late Saturday, before gradually fading from view, according to a time-lapse video from an Alert California camera operated by UC San Diego.