A fire scorches a hilltop near Lake Piru

LOS ANGELES (CNN) -- Southern California's fire season is under way and firefighters are working around the clock battling three wildfires.

The Waterman Canyon fire, burning in the hills above the city of San Bernardino, has consumed 350 acres of brushland. The fire began at about 3:30 p.m. local time, and was 10 percent contained by sundown Tuesday night.

Cooler evening temperatures and winds which are blowing the fire back into itself are expected to help firefighters throughout the night, according to Candace Vialpando of the San Bernardino Forestry Department.

Although there are many homes in the area, no residences are threatened. However, firefighting resources have been mobilized to protect a radio tower which is directly in the path of the fire. Fire officials suspect that downed power lines may have caused the Waterman Canyon fire. They have no estimate on when the fire will be contained.

Firefighters continue to make slow but steady progress fighting two wildfires that have been burning since Sunday north of Los Angeles.

A fire in Ventura County near Lake Piru which has consumed 9,700 acres in three days is now 55 percent contained. Full containment is expected Friday, officials say. There are over 1,000 firefighters currently fighting the blaze.

The Lake Piru fire had caused the evacuation of a condominium complex and school closures. All evacuees have returned to their homes and schools have re-opened. Lake Piru is located in a remote area approximately 20 miles north of Los Angeles.

Another fire, burning in the Los Padres National Forest near Santa Barbara, has scorched 3,500 acres since Sunday. It is now 45 percent contained and full containment is expected Wednesday evening if the weather continues to cooperate.

No structures have been damaged and no residences are immediately threatened. Four firefighters have been injured, two with minor hand injuries, one with a strained back, and another sustained a minor leg injury. Juanita Freel of the National Forest Service said firefighters believe the Los Padres fire started when a farm tractor hit a small rock, causing a spark.