San Diego County crews are traveling north to help battle a wildfire burning in Mariposa County that's threatening homes and the power supply to Yosemite National Park.
Three San Diego Fire-Rescue Department engines along with crews from National City and Chula Vista fire departments left Wednesday to battle the Detwiler Fire.
Mariposa is located approximately 400 miles north of San Diego west of Yosemite National Forest.
Since it started on Sunday, the Detwiler Fire has burned nearly more than 70,000 acres or 109 square miles.
Thousands have been forced to leave tiny, Gold Rush-era towns in the area.
At its closest, the blaze was still about 35 miles from the boundary of Yosemite, where campgrounds are open, park spokesman Scott Gediman said.
Power lines supplying power to Yosemite National Park were threatened.
The fire closed one of several roads into the park during its busy summer season, and rangers warned visitors with respiratory problems to be mindful of the haze, Gediman said.
Yosemite does not appear at risk from the fire, which was moving south Wednesday, away from the park, California fire spokesman Jordan Motta said.
The fire was threatening about 1,500 homes and other buildings, after already destroying 45 structures and damaging six.
The flames are near Highway 49, a historical route winding its way up California foothills of the western Sierra Nevada dotted with little towns that sprouted along the gold Mother Lode that drew miners to California in the 1800s.
Record rain and snowfall in the mountains this winter abruptly ended California's five-year drought. But that has increased the challenge for crews battling flames feeding on dense vegetation.
"There's ample fuel and steep terrain," Cal Fire spokeswoman DeeDee Garcia said. "It makes firefighting difficult."
Gov. Jerry Brown has declared an emergency, bolstering the state's resources to battle the fire that he said has forced thousands of residents to flee and is expected to continue burning.
The cause of the fire was under investigation.
Here are some of the road closures effective Wednesday, July 19:
- HWY 49 N from Smith Rd to Oakridge Rd.
- HWY 140 from Triangle Rd to School House Rd.
- HWY 132 at Horseshoe Bend
- HWY 140 at Yaqui Gulch Rd.