Dense smoke from a wildfire burning in and around Yosemite National Park on Saturday hampered both suppression efforts and the prized views sought by holiday weekend tourists, AP reported. For the first time since the blaze broke out in a neighboring forest two weeks ago, smoke obscured Yosemite Valley, home to the California park's most popular landmarks, spokeswoman Kari Cobb said. "I'm in Yosemite Valley right now, and I cannot see the cliffs around me," Cobb said. "The wind has shifted and smoke is impacting the entire park. We have been lucky until now." All the campgrounds in the Valley still were full as of Saturday morning, despite the thick blanket and burning smell that permeated the area, she said. As a health precaution, visitors were being asked to scale back their outdoor recreation plans and avoid strenuous activities or even stay indoors. Meanwhile, firefighting aircraft remained grounded because of low visibility caused by the smoke, U.S. Forest Service spokesman Mark Healey said. The blaze had scorched 348 square miles (901 square kilometers) of brush, oaks and pines and 11 homes, as of Saturday, an area larger than the cities of San Francisco, Oakland and San Jose combined. Of that total, 94 square miles (243 square kilometers) of wilderness have burned in the northern section of Yosemite, up from 75 square miles (194 square kilometers) a day earlier. The fire was 40 percent contained.