Los Angeles  - Cooler weather on Wednesday helped an army of firefighters gain the upper hand on the largest and most dangerous fire of the year in California.

Fire officials said that the Station Fire north-east of Los Angeles was 22 per cent contained, compared to just 5-per-cent containment a day earlier. They revealed that the fire was human caused but remained unsure whether it was the result of arson, or an accidental ignition from a cigarette, campfire or spark from machinery.

Incident commanders said the fire had burnt more than 56,000 hectares and was being fought by more than 4,100 personnel. Many were stationed at the thousands of homes still threatened by the blaze, while others lit backfires to starve the fire of fuel and constructed huge bulldozer lines to prevent the fire from spreading.

The fire is believed to be the biggest in Los Angeles County in more than 100 years and has destroyed at least 62 homes. Two firefighters have been killed and 14 injured.

But incident commander Mike Diedrich sounded hopeful that the massive firefighting effort was succeeding.

"The crews are making excellent progress based on the improved weather conditions," he said Wednesday.

He warned that a change in wind conditions could easily lead to a flare up.

Visiting the fire's command centre, California Governor Arnold Schwarzenegger pledged that despite the state's budget crisis, money would always be found to keep up a full assault on the fires throughout the season.

He hailed the firefighters and warned that despite the progress over the last day, the danger was far from over.

"Don't relax, because the fires are still out there blazing away," Schwarzenegger said at a press conference. "But the firefighters are doing a great job."

California has already spent almost 60 per cent of a 182-million- dollar fund set aside to cover the cost of firefighting, even though the state is just 20 per cent through the fire season. However, the Federal Emergency Management Agency will reimburse the state for 75 per cent of the firefighting costs, Representative Brad Sherman, a California Democrat, said at the press conference.

The progress in beating back the blaze meant that evacuation orders were lifted for thousands of residents, though 12,000 houses remained under threat. Though the number of homes destroyed is relatively small, the fire is still a huge blow to the Los Angeles region, devastating much of the wilderness area that rings the city.

The threat to Mt Wilson, which houses a historic observatory as well as communications towers that serve Los Angeles television and cellphone providers, receded as fire crews constructed firelines around the site and coated structures with fire retardant gel and foam.

"We are going to burn, cut, foam and gel. And if that doesn't work, we're going to pray," said Fire Department Battalion Chief Steve Martin. "This place is worth a lot, but it's not worth dying for."

Experts said that the fire's damage would have been much worse had it erupted during peak fire season when strong Santa Ana winds, gusting at 100 kilometers per hour, can fan the flames into an unstoppable inferno.

"This could have been like the conflagration of the century with the Santa Anas," Bill Paziert, a NASA meteorologist, told the Los Angeles Times. (dpa)