This is an updated version of a story posted earlier Wednesday afternoon.
LOS ANGELES (AP) - Federal agents joined the search for evidence Wednesday in the brush-covered hills where an arsonist may have ignited one of the wildfires devastating Southern California.

Elsewhere, 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 have burned throughout seven counties, destroying about 1,500 homes and causing more than a half-million people to flee since the first blaze began late Saturday.

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, meanwhile, 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 was deliberately 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.

John Alfred Rund, 48, of Hesperia was arrested late Tuesday after authorities followed him to an address on State Route 173.

Officials said witnesses spotted Rund start a fire in brush on State Route 173 south of Arrowhead Lake Road, then leave on a Honda motorcycle. Authorities said they didn't know if Rund was connected to any of the 16 major wildfires burning in Southern California.

In 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.

The chase started after campus security officers at California State University, San Bernardino, found the man, from Arizona, inside a car in a brushy area near campus, police said.

The officers were concerned and wanted to make sure he wasn't trying to start a fire. When they approached, the man drove off.