SAN FRANCISCO (Reuters) - Firefighters determined to keep a massive blaze from raging into the heart of California's Yosemite National Park have shut down half of its main east-west corridor, just days before a holiday weekend marking the end of the peak summer tourist season.
A long stretch of Tioga Road through the western half of the park was closed on Wednesday as fire crews tightened their grip on the blaze, extending containment lines around 30 percent of the wildfire's perimeter by the end of its 12th day.
The so-called Rim Fire has blackened about 192,500 acres, or more than 300 square miles, of dry scrub and timberlands, mostly in the Stanislaus National Forest west of the park. Its cause is still being investigated.
The firefighting force of more than 4,500 is backed by teams of bulldozers, water-dropping helicopters and airplane tankers carrying payloads of flame-retardant chemicals.
