Blaze near Yosemite National Park started by unattended campfire

An unattended campfire in Mariposa County sparked a blaze that has burned about 1,600 acres, authorities concluded Tuesday.

The Carstens fire broke out Sunday afternoon east of California 140 in the Midpines area, about 40 miles southwest of Yosemite National Park. Investigators will try to track down who was responsible for the campfire, said Cal Fire spokesman Daniel Berlant.

About 800 homes remained threatened by the wildfire, which has closed the primary road leading to Yosemite and drawn more than 2,200 firefighters to fight it. It is 15% contained.

“With the numbers of homes that are threatened and the potential for this fire to grow, we needed to call in those additional resources,” Berlant said.

The fire season has started unusually early this year, officials said. California is experiencing one of its driest years in a century, and the state’s fire forecast is ominous.

“We’re not even in the peak fire season,” Berlant said. “We’re experiencing conditions statewide months earlier than normal.”

More than 51,000 acres have burned across California this year, Berlant said. At this time last year only 19,000 acres had burned. Cal Fire has responded to 2,600 fires so far in 2013, a 75% increase from 2012, he said.

The Carstens fire has been encouraged by warm weather, low humidity and moderate winds, Berlant said. The blaze has run through years-old dry timber and brush toward the Sierra National Forest.

Evacuations have been ordered for areas including Hites Cove, Jerseydale and Clarks Valley, but no structures have been damaged. California 140 was closed at Triangle Road, officials said, and Triangle Road was shut in three additional areas.

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Joseph.serna@latimes.com

@josephserna