Firefighters in Southern California are getting help from cooler weather as they battle stubborn wildfires, which have blackened 200,000 hectares and destroyed at least 1,800 homes. Mike O'Sullivan reports, authorities say arsonists are behind at least two fires, and California Governor Arnold Schwarzenegger has issued them a warning.

Accompanied by state and local officials, Gov. Arnold Schwarzenegger, center, walks to a news conference at the Santiago Fire Incident Command Post at Irvine Regional Park

Authorities are investigating hundreds of leads, including a report of a white pickup truck seen in the area where the Orange County fire started. That blaze destroyed 14 homes.

Five people have been detained on suspicion of arson, but authorities say none has been linked to any of the large fires. One man in Los Angeles pleaded not guilty Friday to a single count of arson.

The number of deaths that resulted directly from the fires now stands at seven. Authorities say four people who were found dead Thursday near the U.S.-Mexico border were killed by fire. They are thought to have entered the United States illegally through a remote canyon.

Cooler temperatures and higher humidity have helped firefighters gain the upper hand against a dozen blazes, which are now contained. Nine fires were not contained by mid-Saturday, and thousands of homes remain threatened.

Many homeowners have returned to their communities to assess the damage and file claims with private insurers or seek emergency aid from the federal or state governments. Mr. Schwarzenegger announced additional grants of up to $10,000 for those affected by the fires, and warned of fraud artists who may try to cheat homeowners. "If anyone tries to exploit this tragedy, I will make sure that the state of California will do anything possible that you will pay for that for the rest of your life," he said.

A smoky haze hangs over much of southern California, and residents in many places were urged to stay indoors because of high pollution levels.