One-fifth of the city's sprawling Griffith Park was a fire-charred landscape Thursday as firefighters extinguished that last remaining hotspots from a wildfire that had threatened its landmark observatory and zoo.

Firefighters had the fire zone close to contained and were working on smoldering tree stumps and clearing away smoky debris.

Cooler nighttime temperatures helped firefighters rein in the 817-acre blaze — the third this year in the urban tinderbox of the Hollywood Hills. Still, officials cautioned that a sudden change in the weather could stoke remaining embers. Fire Capt. Antoine McKnight noted another concern Thursday: Rattlesnakes were emerging as the ground cooled.

Fighting fires in the hills of Griffith Park is especially difficult because of the heavy brush and narrow, twisting roads that weren't designed to accommodate fire engines.

Last month, winds blew a power line down on a hillside, and flying embers damaged or destroyed three homes in neighboring Beverly Hills. In March, authorities said teenage tourists ignited a fire that spread over 200 acres and climbed close to the Hollywood sign before it was extinguished.

"It's only a matter of time until we have a really serious, life-threatening fire on our hands in the hills," fire Capt. Carlos Calvillo said.

Griffith Park is iconic L.A.: It's the Hollywood sign and the backdrop for movie after movie after TV show, with panoramic views of the Pacific Ocean miles away that even the rich can't buy.

For all they share, the park is nothing like the concrete jungle that surrounds it.

It's an undulating expanse of dry wilderness, crisscrossed by hiking trails and roamed by coyotes. Its valleys muffle the round-the-clock drone of traffic on nearby freeways, and some nights feature starlit horseback rides — real stars, not the ones in the tabloids.

Like the nation's other great urban oases, the more than six-square-mile Griffith Park mixes undeveloped swaths with famous landmarks and spaces where the city's diverse population mingles and relaxes. Its dusty soccer fields host Central American soccer leagues on weekends, while several peaks away, a Greek theater is hewn into a hillside.

Aside from the booming white letters that mark Hollywood, its most famous landmark is the Griffith Observatory, where James Dean's character in "Rebel Without a Cause" learned about the solar system.

Now-charred chaparral scrub dots hillsides above the observatory between ridgeline clumps of eucalyptus and pine trees and hard-packed, bone dry trails.

The fire began Tuesday near one of the park's three golf courses amid extremely dry, hot conditions. As it spread, it forced the evacuation of about 150 homes and the closure of the recently renovated observatory, the Greek Theatre and the Los Angeles Zoo, where most of the facility's 1,200 animals waited out the fire and smoke inside holding cells.

Authorities were still trying to determine the cause of the fire Thursday.

They questioned a man who said he had fallen asleep in the park smoking a cigarette and woke up with his shirt on fire. The mayor said the man remained a person of interest, but officials said the fire did not appear to have been intentionally set.

"At this point, there's no indication that it was anything but an accident," said Battalion Chief John Miller.