Reno, Nevada - Lightning bolts sparked another half dozen new wildfires that were burning around Reno and Carson City early Tuesday, worsening the damage from blazes that already have consumed about 50,000 acres of northern Nevada.

More than two dozen fires remained active, many out of control, reaching from the heavily timbered western front of the Sierra Nevada near Reno to the sage- and grass-filled rangeland near Elko, 300 miles east.

In Arizona, a 58,300-acre wildfire north of Grand Canyon National Park jumped the only highway leading to the remote North Rim, closing the road and marooning hundreds of tourists and workers. The fire was burning about 30 miles from the park, but officials said no one was in any danger.

"The canyon is covered in smoke,'' Amber Boeldt of Globe said in a telephone interview from the Grand Canyon Lodge, where she and her family were staying. "That's all you can smell.''

An estimated 200 of the 950 stranded people drove for two hours on a forest to Fredonia, said park spokeswoman Maureen Oltrogge. Crews planned to evaluate conditions Tuesday morning to determine whether it was safe to escort out the remaining people.

As many as 300 homes and businesses east of Carson City in the Mound House area were threatened by a pair of brush fires covering an estimated 1,500 acres that forced the temporary closure of part of U.S. Highway 50.

Nevada officials earlier ordered evacuations in two rural communities near Elko and flames burned within a quarter mile of homes 15 miles northwest of Reno, but no injuries were reported and no homes faced immediate threat. Some residents also voluntarily evacuated from the rural valleys on the northern outskirts of Reno, where some of the new lightning fires that began Monday were burning an estimated 2,000 acres.

Nevada's biggest fire has grown to 40,000 acres about 20 miles west of Elko near Carlin, where the University of Nevada Fire Science Academy is located along I-80.

"We do a lot of real-life fire training, but we never expected this,'' said Denise Baclawski, the academy's executive director. "All night long we had staff members work to protect the facility.''

Northwest of Reno, a 1,500-acre wildfire in the Sierra just across the Nevada-California line was estimated to be 50 percent contained early Tuesday and some of those 250 firefighters were being transferred elsewhere.

About 90 miles north along U.S. Highway 395 near Susanville, Calif., an 100-acre fire forced evacuations of as many as 100 homes before residents began returning Monday night.

Near Sedona, Ariz., fire officials predicted that a 4,200-acre fire that forced hundreds to evacuate would be contained Wednesday. Owners of the roughly 400 homes and scattered businesses still evacuated were expected be allowed to return Tuesday night.

Elsewhere, a 3,200-acre blaze a mile west of the northern New Mexico town of Gallina calmed. Crews were still fighting the fire, though evacuees from 120 homes in three subdivisions were allowed to return Monday.

As of Monday, wildfires around the United States had blackened 3.3 million acres this year, compared with 1.2 million acres on average at this point in the fire season, the National Interagency Fire Center reported. However, much of this year's acreage resulted from huge grass fires in Texas and Oklahoma this spring, not from forest fires.