California Gov. Arnold Schwarzenegger vowed Saturday that authoritieswill "hunt down"thearsonists who started some of the wildfires that havedevastatedhis state's southern region.

arnieinside2-cp-3811767

California Gov. Arnold Schwarzenegger warned Saturday that the arsonists responsible for the Santiago Fire, as well as anyone who commits fraud or tries to take advantage of fire victims, will be prosecuted to the fullest extent of the law. ((Reed Saxson/Associated Press))

"We already know that at least two of the fires were started intentionally, and two more have suspicious origins," Schwarzenegger told reporters at a press conference at the scene of one of the fires in San Diego County.

"I want everyone to understand that we will hunt down the people responsible for that, and we will arrest them and prosecute them to the full extent of the law.

"If I were one of the people who started the fires, I would not sleep soundly right now, because we're right behind you."

Five people have been arrested in arson investigations, but authoritieshave not linked any of them to the larger blazes.

Schwarzeneggeralso warned residents to be on the lookout for scammers and price-gouging, saying crooks are trying to take advantage of people at a vulnerable time.

Some of the worst wildfires sparked a week ago in San Diego Countywere finally dying down Saturday. Across the state, about 1,700 homes have been destroyed, 80 per cent of them in San Diego County, wheredamage is expected to total$1 billion US.

The blazes charred more than 2,000 square kilometres of land and left at least seven people dead.

Health officials warn residents over soot-ridden air

Meanwhile, as residents began returning to theirhomes to assessthe damage,concerns over air quality are growing.

california-fires-cp-3809357

Homeowner Tony Heinrichs looks down at his recovered tool box found inside his destroyed home in the Rancho Bernardo area. ((Damian Dovarganes/Associated Press))

Health authorities have warned that smoke and ash may irritate people's lungs. They have been urging children, the elderly and people with respiratory problems to stay indoors.

Air quality remained poor on the weekend in the central San Bernardino Mountains and parts of the San Bernardino Valley, as well as swaths of Orange and Riverside counties.

"When the fires were burning, there were smoke plumes shooting 10,000 feet into the air and poor air quality is a concern," Carter Evans of CBS News told CBC Newsworld Saturday from San Diego's fire-ravaged Rancho Bernardo neighbourhood.

In San Diego County, where only two of five major fires were more than 50 per cent contained, the air was especially dismal onFriday.

People lucky enough to find their homes still standing could still face hardships for weeks to come because of the polluted air, downed utility lines and an absence of drinking water.

In the town of Ramona, in San Diego County, fire trucks drained the local reservoir that normally supplies water to about 10,000 residents.

San Diego's Qualcomm Stadium was scheduled to close Saturday as an evacuee shelter. The football stadium housed upwards of 10,000 people forced from their homes because ofthe wildfires.

Residents are returning to their neighbourhoods and officials have opened assistance centres in the hardest-hit communities.

With files from the Associated Press