SACRAMENTO, California (Reuters) - Fifty buildings were destroyed by a 21,500-acre wildfire raging in Northern California that has forced the evacuation of about 3,000 people near the small town of Manton, fire officials said late on Tuesday.

Dubbed the Ponderosa Fire, the lightning-sparked blaze roared through brush and heavy timber in Tehama and Shasta counties, about 125 miles north of the state capital Sacramento, since it started on Saturday.

Firefighters were finally able to survey the damage from the air in one of the more heavily populated areas affected, to the southeast of tiny Manton, on Tuesday.

The structures destroyed include not only residential houses but also barns and sheds, but firefighters were not expected to inspect the damage up close and on foot until Wednesday, Chico Fire Division Chief Shane Lauderdale told Reuters.

"There is a good chance that number (of destroyed buildings) will go up, because they haven't been able to get into the whole area affected by the fire," Mike Witesman, a spokesman for the California Department of Forestry and Fire Protection, said.

More than 2,000 fire personnel successfully fought strong winds all day Tuesday to save the neighboring small town of Shingletown from burning, Lauderdale said.

However, more than 200 residences remain threatened by the blaze burning over steep and rugged rural terrain.