Updated 10:01 PM ET
LOS ANGELES - An arsonist swept through the Hollywood area under the cover of dark early Friday, torching vehicles whose flames ignited nearby houses, including one once occupied by Doors frontman Jim Morrison.
The four-hour onslaught started shortly after midnight and sent firefighters scrambling to douse fires in 21 locations in Hollywood and the neighboring city of West Hollywood. In nearly every case, the fire started in a parked car.
Authorities ruled out any possible link to terrorism while bracing for another round of fires and continuing the search for a suspect.
"We are hoping for the best but anticipating and preparing for the worst," Los Angeles City Fire Chief Brian Cummings said.
Los Angeles officials urged continued public vigilance Friday and offered at least $35,000 in rewards for information leading to the conviction of an arsonist or arsonists.
County supervisor Zev Yaroslavsky says the county is offering a $25,000 reward and the federal Bureau of Alcohol, Tobacco, Firearms and Explosives is adding another $10,000 to the reward.
The city council is drafting a motion to add another $25,000 to that sum, but councilman Tom LaBonge urges citizens to come forward with any information they have immediately.
Dozens of people were rousted from their homes, power was disrupted in several neighborhoods and Los Angeles police were put on alert in the Hollywood area. One city firefighter was treated and released from a hospital after a fall from a ladder while battling one blaze. No other injuries were reported.
All of the fires on Friday were in a 2-square mile area and most were in densely populated residential neighborhoods where residents would likely be asleep.
"This is the most dense part of Los Angeles and West Hollywood. We have 20,000 people per square mile living in this area. One fire out of control could cost dozens of lives," said John Duran, mayor of West Hollywood where four of the fires were set.
Authorities were interviewing witnesses and looking for any video footage that may have captured the person, or people, responsible for the spate of crimes. Investigators from four agencies met for a strategy session, while Los Angeles officials summoned investigators from the federal Bureau of Alcohol, Tobacco, Firearms and Explosives.
Mayor Antonio Villaraigosa praised the coordination of the agencies, saying they're "working around the clock to investigate these crimes and they're pursuing every single lead."
We will "be preparing for what may be coming tonight," said Los Angeles County fire Battalion Chief Tom Sullivan.
Fire officials couldn't say whether the rash of fires was the work of a copycat. There was a series of other arson fires early Thursday, also in Hollywood. Two people have been arrested and remain in custody for those blazes, officials said.
One of the homes was in Laurel Canyon, where Morrison and his girlfriend once lived, neighbors said. The winding road was the inspiration for the Doors' hit "Love Street," and the house was listed for nearly $1.2 million earlier this year, according to real estate website Zillow.com.
Sandy Gendel, who owns a nearby restaurant, said he heard explosions from what he later determined were likely car tires. He saw flames 30 feet high coming from the deck of the former Morrison house and a gutted Mazda Miata.
"It was just like a towering inferno," Gendel said.
Jeff Dorman, who lives in the neighborhood, said he and his wife were awakened by noise in the street.
As he and his neighbors watched the firefight, he said they worried about embers floating toward their houses because they are so close together. They also were concerned about a firebug being loose in their neighborhood.
"One spark could have been a huge problem," Dorman said. "The fire department did a fantastic job."
One fire destroyed four cars at a single apartment complex, reports CBS Los Angeles.
City Councilman Tom LaBonge said the arsonist is mostly targeting underground parking in mid-century type apartments that have no security gates and putting some kind of incendiary device under cars.
"These are not trash can fires on street corners. We are just a second away from tragedy," he said.
Los Angeles Fire Department spokesman Jaime Moore said car fires spread to adjacent buildings in at least three cases, and investigators were looking for patterns that might link the blazes.
Hollywood is served by the Los Angeles city police and fire departments. Adjacent West Hollywood is a separately incorporated city served by the Los Angeles County fire and sheriff's departments.