Power, water in San Francisco threatened as Rim Fire enters Yosemite SAN FRANCISCO, Aug. 24 (UPI) -- California Gov. Jerry Brown declared a state of emergency in San Francisco as the Rim Fire threatened power lines 150 miles away in Yosemite National Park. The governor's concern was heightened as ash from the massive fire endangered the quality of the city's water supply from Hetch Hetchy, the San Francisco Chronicle reported. The blaze has blackened nearly 200 square miles, doubling in size in the space of a day, but firefighters were optimistic of progress. By Friday evening, the wildfire was 5 percent contained, said Daniel Berlant of Cal Fire, a dramatic increase from the 2 percent earlier in the day. The fire, which had blackened 53,000 acres on Thursday, grew to nearly 126,000 acres late Friday night, CNN reported. It began Aug. 17 in the Stanislaus National Forest. Some 2,700 firefighters from across the United States are involved in containing the fire. Their efforts have been hampered by having to work in steep and largely inaccessible terrain. Pine Mountain Lake's 2,800 mostly seasonal residents had been ordered to evacuate. Two smaller nearby towns, Groveland and Tuolumne City had been advised, but not ordered, to leave. More than 5,500 homes are threatened; four have been destroyed. Yosemite officials shrugged off the possibility the park might have to close. "If it continues to move in the direction it has in the last day or so, it's just moving into wilderness," said Kari Cobb, a park spokeswoman. There's no structures, nothing there. Smoke from the wildfire has blown into Nevada, lowering air quality to unhealthy levels, the Reno Gazette-Journal reported. The Washoe County Health District measured air pollution levels at 200, one point less than "very unhealthy." Schools and parks across the area canceled outdoor activities. The number of people reporting to the emergency room of Reno's hospital with breathing difficulties had increased significantly since Thursday, said a hospital spokeswoman. In Montana, some 20 families in recreational vehicles have been camped out since late Tuesday in a shopping center parking lot after the Lolo Creek Complex wildfire threatened their lakeside campsite, The Missoulian reported. The campers have been told they may be able to return by Sunday or Monday.