(CNN) -- Officials are searching for the driver of a white truck seen on Santiago Canyon Road on Sunday, near the time the Santiago fire started, Orange County authorities said Friday.

Chief Chip Prather holds a photo of a white truck similar to the one seen on Santiago Canyon Road. more photos »

"These people are not suspects at this time," Orange County Fire Authority Chief Chip Prather said. "They are persons of interest who were seen near the fire in a vehicle like this."

The vehicle is a white, 1998 to 2004 Ford F150 pickup with chrome tubular running boards.

Prather said the information came from a lead called into the investigation's tip line.

A $250,000 reward has been offered for information leading to the arrest of the person or persons responsible for the blaze. Watch how residents feel about arsonist »

The Santiago fire, now 27,000 acres and still burning, was deliberately set, officials said Thursday.

Several mandatory evacuations remain in place for the Santiago fire, which has destroyed 14 homes and various other structures. Late Friday afternoon, the blaze moved into Silverado Canyon, authorities said. Sheriff's deputies were evacuating residents in the fire's path. Watch the Santiago flames rage »

Authorities also suspect arson in the Rosa fire in San Diego County, which burned more than 400 acres before being fully contained. There was no information on the investigation.

Elsewhere, the Los Angeles County District Attorney's Office filed arson charges Friday against a 41-year-old Sun Valley man who witnesses said set a fire in the West Hills neighborhood and walked away.

Catalino Pineda is one of five people who have been arrested in arson investigations this week, but none of them has been linked to the major wildfires raging across Southern California.

Pineda was arrested Wednesday after witnesses said they saw him lighting a fire on a hillside, police said. The fire was quickly extinguished. The witnesses followed Pineda to a nearby restaurant and called police, who arrested him.

Pineda was expected to be arraigned in Van Nuys Superior Court Friday, Deputy District Attorney Steven Frankland said. He is charged with one count of arson of a structure or forest.

Pineda is being held on $75,000 bail and faces up to six years in prison if convicted.

In San Bernardino, east of Los Angeles, John Rund, of Hesperia, was arrested Wednesday on arson charges after a witness reported seeing him in brush near the starting point of a fire Tuesday, the sheriff's department said. That fire was quickly put out by passers-by.

Investigators are trying to determine if Rund, 48, may have ties to other wildfires. He is being held on $750,000 bail.

The San Bernardino County District Attorney's Office on Thursday filed arson charges against Anthony Riperti, 47, of Redlands. A statement from the office did not say when or where Riperti is accused of setting a fire. He is being held on $250,000 bail.

In San Diego County, the sheriff's department this week arrested an adult and a juvenile allegedly seen by an anonymous tipster starting a fire in Vista in the northern part of the county. In a written statement, the sheriff's department identified the adult as Gorgonio Nava. The Vista fire Department extinguished the blaze before it grew out of control, the statement said.

Investigators have determined that the Grass Valley fire in San Bernardino County was not caused by arson, and a preliminary investigation into the cause of the 11,675-acre Slide fire seems to indicate arson was not a factor, sheriff's spokeswoman Cindy Beaver said.

More than 1,600 homes have been destroyed in the past week by Southern California wildfires. E-mail to a friend

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