Nearly 300 firefighters remained on the job Saturday battling the remnants of two wildfires that menaced parts of the city.

Three teenagers had been arrested and accused of setting the first of the two fires that burned along the Rio Grande (search) this past week.

Investigators said that fire, estimated at 75 percent contained, was started by a firecracker tossed into a pile of the cottony seed fibers from cottonwood trees. It burned 352 acres Tuesday and forced the evacuation of hundreds of people as it raced north through the heavily wooded river bottom area.

No arrests had been made in the second fire, which was started Wednesday about a mile from the first blaze, authorities said. It burned 165 acres and forced some 200 people from their homes.

Elsewhere, fire crews were still on active duty Saturday battling flames in California and Arizona.

About 150 miles north of Los Angeles, crews had contained 90 percent of a 540-acre blaze that burned a small house, a cabin and other buildings near Lake Isabella (search), said U.S. Forest (search) Service spokeswoman Margie Clack.

Firefighters had the fire about 80 percent contained Friday, but wind fanned the flames past their firebreaks.

By late Saturday, a voluntary evacuation order for 120 homes was lifted and two campgrounds reopened, Clack said. A six-mile stretch of state Highway 155 also was reopened.

Officials in southern Arizona estimated Saturday that the human-caused fire that burned through a vacation community atop Mount Lemmon (search), outside Tucson, cost $7.2 million to fight. Investigators said they still had no suspects in the blaze.

The wildfire was 50 percent contained after burning across 34,000 acres and destroying 317 homes or cabins and seven businesses in the community of Summerhaven, officials said Saturday. It began June 17.

On Saturday, firefighters were concentrating on the southwest corner of the Mount Lemmon fire.

"It's the most dangerous place in the fire," said fire spokesman Jason Kirchner. "There's no place to deploy a fire shelter because of lots of steep canyons and large rocks."