SAN DIEGO (AP) — A man was charged with setting one of nearly a dozen fires that have destroyed homes and raced through nearly 20,000 acres of northern and eastern San Diego County brush land, but most of the blazes seemed to be dying down.

Thousands of firefighters and fleets of water-dropping military and civilian helicopters planned fresh battles Saturday, including three fires at the Camp Pendleton Marine base.

All together, the wildfires about 30 miles north of San Diego have caused more than $20 million in damage.

Investigators continued to seek the causes of the fires that burned at least eight homes and an 18-unit condominium complex, emptied neighborhoods and spread fields of flame and ash that dirtied the air in neighboring Orange County and as far north as Los Angeles County.

Alberto Serrato, 57, pleaded not guilty Friday to an arson charge in connection with one of the smaller fires, a 105-acre fire in suburban Oceanside that started Wednesday and is fully contained.

Tanya Sierra, a spokeswoman for the San Diego County district attorney’s office, said witnesses saw Serrato adding dead brush onto smoldering bushes, which flamed up. He has not been connected to any other fire, Sierra said.

Oceanside police Lt. Sean Marshand said Serrato is believed to have added fuel to the fire but not to have started it.

“Unfortunately we don’t have the guy that we really want,” he said.