Firefighters up containment of California wildfire that has burned over 4,000 acres

Firefighters battling a raging wildfire in Malibu, California, significantly increased containment on the blaze Thursday after it spread to over 4,000 acres, destroying homes and leaving more than 20,000 people under evacuation, including 98-year-old Dick Van Dyke and other celebrities in the oceanfront community.

The Franklin Fire, which erupted Monday night near the campus of Pepperdine University, was 20% contained as of Thursday afternoon, up from 7% Wednesday night. More than 1,900 firefighters are battling the blaze in the rugged and hilly terrain of Malibu Canyon, according to the California Department of Forestry and Fire Protection (Cal Fire).

Burning through thick dry vegetation, the fire has been fueled by Santa Ana winds that have topped 90 mph, officials said.

"Firefighters are taking advantage of the cooler weather and higher humidities to gain containment and strengthen fire lines around the fire," Cal Fire said in an update Thursday.

Red Flag warnings issued by the National Weather Service signaling the high risk of fire danger had all expired.

In a message posted on his Facebook page, Van Dyke, who is set to turn 99 on Friday, said he and his wife, Arlene, were forced to evacuate as flames threatened their home in the secluded community of Serra Retreat in the hills of lower Malibu Canyon. He said all of his pets, except for his beloved cat Bobo, managed to escape.

On Thursday, Van Dyke posted an update on Facebook saying his cat was found alive when he and his wife were allowed to return home.

"We found Bobo as soon as we arrived back home this morning," Van Dyke wrote. "There was so much interest in his disappearance that Animal Control was called in to assist. But, thankfully he was easy to find and not harmed."

Other celebrities residing in the area were forced to flee the flames or stay on lockdown. Recent Rock and Roll Hall of Fame inductee Cher also evacuated, according to her publicist.

"Star Wars" actor Mark Hamill said in an Instagram post that he has also been affected by the fire.

"We're in lockdown because of the Malibu fires," the 73-year-old Hamill said in the post. "Please stay safe everyone! I'm not allowed to leave the house, which fits in perfectly with my elderly-recluse lifestyle."

The Franklin Fire erupted just before 11 p.m. Pacific time on Monday and quickly grew amid the blustery Santa Anna winds, which blow southwest toward the Pacific Ocean.

At least seven homes have been destroyed by the fire and another eight have been damaged, according to Cal Fire.

Power to about 40,000 customers was shut off by Monday night, including 11,000 in Los Angeles County, as Southern California Edison worked to mitigate the impacts of the Santa Ana winds, whose strong gusts can damage electrical equipment and spark more wildfires.

There have been no reports of deaths or injuries. The cause of the fire remains under investigation.

Pepperdine University canceled classes on Tuesday and Wednesday. When the fire erupted, officials put the campus on lockdown for about six hours before the order was lifted. As the fire grew on Tuesday, students were again ordered to seek shelter in the campus center and library, where students said they watched flames creep onto campus.

"The Franklin Fire continues to burn in the Santa Monica Mountains but is no longer near or threatening the Malibu campus. The weather has improved considerably from a fire perspective. Winds are relatively calm, and the red flag warning has ended," the university said on its website on Thursday.