Assisted by rising humidity and dipping temperatures, firefighters managed to slow the spread of a wildfire in northern Los Angeles, fire commanders said on Wednesday.

Los Angeles County firefighters spray water to put out hot spots after setting a tactical backfire during the Station fire in the Glendale area of Los Angeles, California September 1, 2009. [Xinhua/Reuters Photo]

The Station Fire has grown by another 13,000 acres (5,265 hectares) overnight, but its spread was being contained, said Capt. Mike Dietrich, the Station Fire incident commander.

As "excellent progress" was being made, the fire no longer posed an immediate threat to Mount Wilson, site of an historic observatory and radio and television transmission towers.

The fire, which broke out near a ranger station in the Angeles National Forest a week ago, has now churned through 140,150 acres (56,760 hectares), is now 22 percent contained, Dietrich told a press conference.

"Crews last night continued to work on all perimeters of the fire. The crews are making excellent progress, based on the improved weather conditions that we've experienced temporarily through the night," Dietrich said, referring to increased humidity, which was at the 50 percent level Tuesday night.

The blaze killed two firefighters, destroyed 62 homes and three commercial buildings and, to date, has cost 21 million dollars to battle, Dietrich said.

A general view of the Angeles Forest National Mill Creek Ranger Station in ruins after day seven of the Station Fire September 1, 2009. [Xinhua/Reuters Photo]

Dietrich said the fire zones and portions of Los Angeles now look "really good," and several strike teams and fire engines assigned to those areas will be released and allowed to return to their stations.

But Dietrich said some 12,000 homes and 500 commercial were still threatened by the fire.

"Are we out of the woods? No. Have we turned the corner? No," Dietrich said. But he added that fire commanders can now see a "warning sign" that a curve was up ahead.

Firefighters planned "aggressive" air and ground assaults Wednesday to expand containment lines around the fire and protect the structures it threatens.