A huge wildfire near Yosemite National Park in California has continued to threaten San Francisco's water supply, while firefighters warned it was so hot that it could send sparks into new, untouched areas.
The fire, covering more than 230 square miles and burning near one of the country's most popular national parks, edged closer to a the source of San Francisco's drinking water and to some of the giant sequoia trees that are among the largest and oldest living things on earth. They can resist fire but were being sprinkled for protection.
The fire is now one of the biggest in California history, helped by inaccessible terrain, strong winds and bone-dry conditions.
Strong winds threatened to push the blaze closer to nearby communities. About 4,500 structures remained under threat.
"This fire has continued to pose every challenge that there can be on a fire," said a spokesman with the California Department of Forestry and Fire Protection.
The extremely dry conditions have been caused by a lack of snow and rainfall this year. Investigators are trying to determine the cause of the fire.
The tourist mecca of Yosemite Valley remained open, clear of smoke and free from other signs of the fire that remained about 20 miles away.