* Blaze has consumed area the size of Chicago
* Fight focusing on new front in foothill area of homes (Recasts with fire declared to be arson, other details)
By Dan Whitcomb and Steve Gorman
LOS ANGELES, Sept 3 (Reuters) - A huge wildfire burning in the mountains above Los Angeles, now the largest ever in the county, was started by arson and will be investigated as a homicide, authorities said on Thursday.
The so-called Station Fire has killed two firefighters, destroyed 64 homes and torched an area the size of Chicago in the nine days it has roared across the rugged San Gabriel Mountains overlooking Los Angeles.
“After a forensic examination at the point of origin, arson investigators have concluded that the Station Fire was the result of an act of arson,” U.S. Forest Service Commander Rita Wears said.
The deaths of Los Angeles County Fire Capt. Ted Hall and firefighter Arnaldo Quinones, who were killed when their vehicle plunged 800 feet (244 metres) from a road, made the case a homicide, Wears said.
Authorities did not offer details about how the fire was started but an area near the city of La Canada-Flintridge, north of Los Angeles, has been cordoned off with yellow crime scene tape since Wednesday.
It was not clear if any suspects had been identified.
As of Thursday evening, the Station Fire had blackened 145,000 acres (59,000 hectares), or about 226 square miles (585 sq km), making it the largest wildfire recorded in Los Angeles county. It could ultimately become one of the top 10 in state history, in terms of size.
Authorities estimated containment of the massive conflagration at 38 percent, up from 28 percent a day earlier, according to fire commander Mike Dietrich, who said his force of more than 4,700 firefighters was making “great progress.”
By Wednesday night, the all-clear had been given for the last of 6,400 evacuated households to return home.
But a flare-up in one canyon early on Thursday led officials to order a small cluster of homes evacuated, and crews were concentrating their attack on the southeastern flank of the blaze to prevent flames from spreading.
One town on the fire’s southeastern fringe is Pasadena, known for its annual New Year’s Day Rose Bowl college football game and Tournament of Roses Parade. Fire commanders planned to brief residents in a meeting Thursday night.
Fire commanders said Mount Wilson, an observatory and telecommunications and broadcasting hub, would be spared.
The Station Fire has cost $21 million so far to fight, making it the most expensive of several California wildfires in recent weeks that already have depleted the cash-strapped state’s emergency firefighting budget by more than half.
Governor Arnold Schwarzenegger has insisted the state has plenty of resources at its disposal for such emergencies. (Editing by Doina Chiacu)