US police hunt alleged cop killer in mountain cabins

US police hunting a former cop accused of three killings said Friday he may have taken refuge overnight in an abandoned cabin above a snow-bound ski resort, although there is still no sign of him.

More than 100 officers have been searching since Thursday for Christopher Dorner, 33, who has threatened in a chilling online manifesto to target police officers and their families in revenge for his sacking five years ago.

The manhunt continued overnight, when heavy snow began falling in and around Big Bear, two hours east of Los Angeles, with a couple of reported sightings but still no sign of Dorner, described as armed and "extremely dangerous."

"We're going to continue to search primarily up in the mountain area to make sure. There's a lot of cabins up there that are abandoned," San Bernardino County Sheriff John McMahon told a morning briefing.

"We want to make sure he didn't find a place to hide out for the night. Once we exhaust that we'll continue to reevaluate what we're going to do next," he told reporters.

California authorities launched a massive manhunt Thursday for Dorner, suspected of killing a couple on Sunday, before ambushing two policemen early Thursday, killing one. He also injured another officer in a separate incident.

In an Internet manifesto threatening police and their families, former LA Police Department (LAPD) officer Dorner pledged to "bring unconventional and asymmetrical warfare to those in LAPD uniform whether on or off duty."

The LA Police Department, backed by agencies including the FBI, is protecting over 40 possible targets, some of them identified in the "rambling" online manifesto by Dorner, a US Navy reservist.

Dorner's wallet and an ID badge were found early Thursday in San Diego, two hours south of Los Angeles, police said, while there were also reports of police searches in neighboring Nevada, where he has a house near Las Vegas.

Authorities in Big Bear put schools and a ski area on lockdown after the pickup truck matching the description of Dorner's was found in nearby woods. Schools remained closed Friday.

McMahon said he was confident that footprints found leading away from the burnt-out truck were Dorner's.

"They did lead around in that wooded area where the truck was found. We continued to follow them until we lost them where the ground got frozen. We couldn't continue to track," he said.

To cope with the snowy conditions, police were using Snowcats and armored personnel carriers with snow chains on, he said.

Dorner posted his manifesto online Monday, saying he was not afraid to die because he had already in effect died when he was dismissed in September 2008 for making false statements about his training officer.

"I never had the opportunity to have a family of my own, (so) I am terminating yours," he wrote to Quan.

"Suppressing the truth will (lead) to deadly consequences for you and your family. There will be an element of surprise where you work, live, eat and sleep," he added, referring to Quan and several others.

Dorner is described as black, six feet (1.80 meters) tall and 270 pounds (120 kilograms) in weight.

LAPD assistant chief Mike Moore traveled up to Big Bear to join the manhunt, which involved officers from several other forces. "This complex and violent investigation has led to this mountain," he said.

LAPD chief Charlie Beck said on Thursday that Dorner's police and military training made the threat all the more serious.

"He knows what he's doing. We trained him... he's also a member of the armed forces," Beck said. "It is extremely worrisome and scary."