The deadly wildfire in Northern Los Angeles remained active on the southeastern flank in the San Gabriel Wilderness on Monday, fire officials said.

With the fire 51 percent surrounded, firefighters said they hoped to hem in defensible fire lines and drown the active flames with water and retardant drops, the National Forest Service (NFS) said.

On Sunday, helicopters and air tankers made drops on various parts of the Station Fire as firefighters in the Angeles National Forest attempted to tighten the noose on arson-caused fire that started Aug. 26, despite heavy smoke continuing to pour out to the northeast, said the service.

"Fire behavior was moderated today by an aggressive air campaign and improved weather conditions," according to a NFS fire update.

To the fire's northeast flank in the Antelope Valley, facilities at Little Rock Reservoir and scattered houses and ranches at Juniper Flats remain among the 5,000 structures threatened by the flames, the service said.

No evacuations were in effect on Monday.

Since it broke out late last month, the fire has:

-- destroyed 78 homes, mostly cabins, two commercial properties and 86 outbuildings;

-- denuded some 246 square miles (about 394 square kilometers) of forest land;

-- led to the deaths of two firefighters whose truck plunged off a mountain road;

-- injured 10 people, including firefighters and civilians, and

-- cost 49.5 million dollars so far to fight.

Thousands of fire personnel from across the state and region were expected to spend Labor Day Holiday on fire lines.

A full complement of firefighting aircraft, including Super Scoopers leased from Canada, were standing by if needed. Water- and retardant-dropping helicopters and planes were instrumental in keeping the inferno from taking out key broadcast transmitter sites on Mount Wilson, also home to a historic observatory.

The California government has authorized a 100,000-dollar reward for information leading to the fire starter. Investigators have said an accelerant was found near the point of origin. It's unknown what accelerant was allegedly used.

Prosecutors are likely to seek homicide charges if the firebug is ever found.

Air quality has improved in foothill areas near the Station Fire, but localized areas of smoke may cause unhealthy air quality at times in portions of the San Gabriel Valley and San Gabriel Mountains, the South Coast Air Quality Management District (AQMD) reported Sunday.

Residents in those areas should continue to avoid any vigorous exercise and children, the elderly and those with respiratory issues should remain indoors, according to the AQMD.

The projected full containment date is still Sept. 15, but firefighters could get it surrounded a few days earlier, officials said.

(Xinhua News Agency September 8, 2009)