A fire truck drives past burning trees as firefighters battle the Rim Fire near Yosemite National Park, Calif., Aug. 26, 2013.
Authorities in the western U.S. state of California say firefighters have contained 20 percent of a massive wildfire that is threatening a famous national park.
The U.S. Forest Service said Tuesday firefighters in the so-called Rim Fire's northwestern part have successfully laid down a dozer line, which exposes the topsoil and prevent fires from spreading. The Rim Fire stretches more than 652 square kilometers.
Nearly 3,700 firefighters have been deployed to battle the blaze, which has consumed more than 72,000 hectares of land, including part of Yosemite National Park. Their efforts have been hampered by strong winds, high temperatures and extremely dry conditions.
The massive fire has destroyed at least two dozen homes and businesses. It is also threatening the reservoir that provides drinking water for the nearby city of San Francisco. Mandatory evacuations are in place in at least two areas.
Firefighters Battle Massive California Wildfire
1/13A Hotshot fire crew member rests near a controlled burn operation at Horseshoe Meadows, as crews continue to fight the Rim Fire near Yosemite National Park in California, Sept. 4, 2013. (U.S. Forest Service, Mike McMillan)
2/13Crews clear California Highway 120 of debris, as crews continue to fight the Rim Fire near Yosemite National Park in California, Sept. 4, 2013. (U.S. Forest Service, Mike McMillan)
3/13A member of the Monterey Hotshots carries a gas can near a burn operation on the southern flank of the Rim Fire near Yosemite National Park in California, August 30, 2013. (U.S. Forest Service)
4/13A member of the BLM Silver State Hotshot crew using a drip torch to set back fires on the southern flank of the Rim Fire in California, August 30, 2013. (U.S. Forest Service)
5/13A member of the Bureau of Land Management Silver State Hotshot crew from Elko, Nevada, walks through a burn operation on the southern flank of the Rim Fire near Yosemite National Park in California, August 30, 2013. (U.S. Forest Service, Mike McMillan)
6/13Firefighter Russell Mitchell monitors a back burn during the Rim Fire near Yosemite National Park, California, August 27, 2013.
7/13A videographer records the Rim Fire burning through trees near Yosemite National Park, California, August 27, 2013.
8/13A firefighter stands on top of a fire truck at a campground destroyed by the Rim Fire near Yosemite National Park, California, August 26, 2013.
9/13A fire truck drives past burning trees as firefighters continue to battle the Rim Fire near Yosemite National Park, California, August 26, 2013.
10/13South Korean army soldiers demonstrate their martial arts skills during the 66th anniversary of Armed Forces Day at the Gyeryong military headquarters in Gyeryong.
11/13A helicopter reloads fire retardant as firefighters continue to battle the Rim Fire in Tuolumne City, California, August 26, 2013.
12/13South Korean army soldiers demonstrate their martial arts skills during the 66th anniversary of Armed Forces Day at the Gyeryong military headquarters in Gyeryong.
13/13Firefighter A.J. Tevis watches the flames of the Rim Fire near Yosemite National Park, California, August 25, 2013.
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The reservoir is also the source for three hydroelectric generating stations that supply electricity for San Francisco's public facilities. City officials shut down the generators last week, and are buying electricity from other sources to make up the difference.
The cause of the fire that broke out August 17 is under investigation. It is one of about 50 large wildfires burning in the western United States, which has been plagued by a lack of snow and rainfall this year.
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