The ex-cop suspected in the killings of an officer and two others remained at large Friday as darkness fell over a mountain forest and police suspended their manhunt until Saturday morning.

"Once it gets dark out there and the snow keeps falling and they have no air support, I don't know how effective they would be in that situation," spokeswoman Cindy Bachman of the San Bernardino County Sheriff's Department said.

Throughout Friday, more than 100 officers searched through fresh snow for clues to the whereabouts of Christopher Jordan Dorner, 33, a fired Los Angeles Police Department officer and former Navy lieutenant suspected in the three killings.

Dorner allegedly wrote a manifesto declaring a war of revenge on police, authorities said.

By Friday night, police were expected to have completed a search of vacant cabins in the snowpacked forest of the San Bernardino Mountains near the resort town of Big Bear Lake, Bachman said.

Police on Thursday searched 400 homes in the Big Bear Lake area and were completing searches of 200 more on Friday, she said. Overnight patrols in the town were to be beefed up with 12 extra two-officer teams, she said.

"The search is continuing," Bachman said. "First of all, they have to rest. They have been going at this for two days."

Police teams were dressed in snow gear, holding the trigger guards on their assault-style rifles while scouring eight square miles near Big Bear Lake, a popular skiing area two hours east of Los Angeles.

The mountains were the focus of Friday's search effort because police had found Dorner's burned-out pickup truck a day earlier near the resort community.

The truck had a broken axle, which would have prevented the vehicle from moving, and footprints appear to show that Dorner doubled back into the community, said a source with knowledge of the investigation.

It was unclear where Dorner may have gone from there or by what means, the source said.

But Bachman told reporters Friday: "The possibility exists that he is here, somewhere in the forest, so we're going to keep looking...until we determine that he's not here."

Guns found in the truck were also burned, but authorities believe Dorner may have as many as 30 guns with him, the source said. Dorner was in the Navy and is trained in counterinsurgency and intelligence, the source said.

Two inches of snow Friday coated the mountaintop pine trees and roads around Big Bear Lake, leading motorists to use tire chains. Up to six more inches were expected. But the snow was regarded as a godsend because tracking a man on the run would be easier, authorities said.

Despite the intense search, authorities allowed nearby ski resorts to remain open Friday because they don't believe Dorner is in Big Bear Lake. At one point, a smiling snowboarder whizzed by police and media, seemingly oblivious to an ongoing news conference and the seriousness of the manhunt.

Jay Obernolte, mayor of Big Bear Lake community, described Friday as having "a beautiful winter morning." Residents weren't fearful, he said, adding that "many of the people here are armed."

"Is there panic in our community?" Obernolte asked reporters rhetorically. "No, there is no panic. We're a hardy people in the San Bernardino Mountains."

San Bernardino County Sheriff John McMahon said the snowfall slowed some searching done by foot, but police pushed onward.

"The snow is great for tracking folks, as well as looking at each individual cabin to see if there's any sign of forced entry," McMahon said.

"We're going to continue searching until we either discover he left the mountain or we find him," he added. "It's extremely dangerous."

The county jail in downtown Los Angeles was in lockdown Friday as a precaution after a civilian female employee of the Twin Towers Correctional Facility spotted someone fitting Dorner's description, said Los Angelese County sheriff's spokesman Steve Whitmore.

U.S. Navy installations throughout California and Nevada were "maintaining a heightened security posture," a U.S. military official told CNN.

"Security personnel are on the lookout" for Dorner, the official said. The measure was ordered overnight by Rear Adm. Dixon Smith, commander of the Navy's southwest region.

The official declined to discuss security procedures, but said the move was made after it became clear that Dorner earlier this week gained access to the Naval Base at Point Loma and stayed in a motel there.

Two sailors reported that he approached them Wednesday and spoke with them for about 10 minutes. The conversation took place at a coastal "riverine" unit in San Diego where Dorner served in 2006. As a Navy reservist, Dorner held security jobs with that unit.