WYNOLA, Calif. -- More than 850 firefighters were battling a wildfire in the heavily forested back-country wilderness near Julian Wednesday, according to the California Department of Forestry.

Authorities said the fire scorched more than 600 acres.

The blaze was 30 percent contained as of 8 a.m., and four structures on Volcan Mountain were confirmed destroyed, said CDF Information Officer Gary Eidsmoe.

No homes or commercial structures were threatened, and "the fire is moving away from populated areas" in a northeasterly direction, said CDF spokeswoman Roxanne Provaznik.

It was unclear what sparked the blaze, which erupted shortly before noon Tuesday in the Wynola area of San Diego County's eastern highlands, a CDF dispatcher said.

Crews labored through the night to surround the rugged burn area, but there was no estimated time for full containment, the dispatcher said.

The blaze broke out near the site of the 62,000-acre Pine Fire, which consumed dozens of residences in August 2002.

A total of 863 firefighters from the CDF and U.S. Forest Service and volunteer fire departments were battling the blaze, Provaznik said.