The Carpenter 1 fire on Mount Charleston and the Bison Fire in Carson Valley -- both sparked by storms last week -- are not expected to be contained until next week, firefighters said Tuesday.
The Carpenter 1 fire has grown to 15,000 acres, the U.S. Forest Service says, and threatened more than 500 homes and structures, WWVU-TV, Las Vegas, reported.
A mandatory evacuation order has forced nearly 500 people to seek shelter, with some going to a Red Cross shelter at an elementary school.
Officials said the fire has been 15 percent contained.
The Bison Ridge blaze has consumed more than 23,000 acres, the Reno Gazette-Journal reported.
The fire has blackened dense stands of juniper and pinyon in the Pine Nut Mountains.
A few structures that were part of the early 20th century Slater mine were burned on property owned by the U.S. Bureau of Land Management but no other structures were reported to be in danger.
The blaze has been fanned by "erratic" winds, Fire Information Officer Dorothy Harvey said.
Officials said they hope to contain the Bison Fire by July 15. The fire was 25 percent contained Monday night.