(Adds revised figures, evacuation orders lifted, details throughout)
By Marty Graham
SAN DIEGO, May 14 (Reuters) - California fire crews were gaining ground late on Tuesday on a wind-whipped wildfire that blackened more than a square mile in San Diego county, allowing authorities to lift thousands of evacuation orders in the area.
No injuries have been reported and no homes damaged in the blaze, officials said. The cause of the fire, which erupted on Tuesday morning amid temperatures above 100 Fahrenheit (38 Celsius) and high winds, remained unclear.
The so-called Bernardo fire comes as California enters its peak fire season in the midst of one of its worst droughts in decades, setting the stage for what state officials worry could be a particularly intense and dangerous year.
"That's the problem, we have increased temperatures, low humidity and very high winds that are fanning the flames and pushing fire along," said Lynne Tolmachoff, a spokeswoman for the California Department of Forestry and Fire Protection.
Shortly after nightfall, authorities lifted countywide evacuation orders and schools that had been evacuated were expected to resume classes on Wednesday, San Diego Fire Chief Javier Mainar told an evening press conference.
The fire burned some 800 acres, though winds that were gusting up to 25 miles per hour earlier in the day were dying down, making the work easier for firefighters scrambling across tough terrain, Mainar said.
At its peak, hundreds of firefighters, assisted by water-dropping aircraft, fought to keep the flames from advancing into San Diego neighborhoods, officials said.
The Bernardo fire snaked through brush-filled canyons that punctuate the area of upscale homes and gated communities that sit on the mesas above the burning canyons.
California officials have kept staffing levels for wildland firefighters at elevated levels since last year because of the drought.
Officials made more than 20,000 evacuation calls to residences, businesses and mobile phones, the San Diego County Emergency Site said on Tuesday afternoon.
However, San Diego city and county officials told an evening news conference only about 5,000 evacuation notices had been issued. (Reporting by Marty Graham in San Diego and Dan Whitcomb in Los Angeles; Writing by Eric M. Johnson; Editing by Gareth Jones)