LOS ANGELES — Federal agents joined the search for evidence Wednesday in brush-covered Orange County hills where an arsonist is believed to have ignited one of the wildfires devastating Southern California.

In San Bernardino County, a man suspected of starting a small fire was arrested and another man was shot to death by police after he fled officers who approached to see if he might be trying to set a fire.

Wildfires, burning in seven counties, had destroyed about 1,500 homes and caused more than a half-million people to flee since the first blaze began late Saturday. At least two — in Orange and Riverside counties — have been linked to arson.

Throughout the region, authorities stepped up patrols in hopes of preventing copycat fires and looting. In San Diego County, sheriff's officials have reported scattered instances of looting in fire zones. Two people have been arrested.

Orange County officials converged on a remote area of bone-dry brush where a 19,200-acre wildfire has destroyed nine homes. They were aided by special teams from the FBI and federal Bureau of Alcohol, Tobacco, Firearms and Explosives. The federal government planned to send more agents from around the country to help with the probe.

Investigators taped off an area they called a crime scene, took photos, collected evidence and recorded map coordinates, according to ATF Special Agent Susan Raichel. Authorities believe the fire had been set because they found three different ignition points within a short distance — a common sign of arson.

A $70,000 reward was offered for information leading to an arrest in the case.

In San Bernardino County, a motorcyclist who authorities say set a small fire in a rural foothill area of the San Bernardino Mountains has been booked for investigation of arson. Authorities said they didn't know if the man was connected to any of the 16 major wildfires burning in Southern California.

In the city of San Bernardino, police shot and killed a man who fled when officers approached to see if he might be trying to set a fire.

The man, whose name was not released, was shot Tuesday night following a chase that ended when he backed his car into a police cruiser and an officer opened fire, San Bernardino police said.

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Contributing: Associated Press writer Matt Apuzzo in Washington