A former US police officer wanted as a suspect in three murders continues to elude a manhunt in the snow-swept mountains east of Los Angeles.
Search teams combed hillsides and homes around a ski area through the night and past daybreak for Christopher Dorner, 33.
The former Navy officer is presumed by police to be heavily armed and intent on carrying out a vendetta against those he blames for his 2008 dismissal from the LA Police Department.
Snowfall forced authorities to ground helicopters to scour the area with infra-red cameras.
But a team of more than 100 law enforcement officers, some of them riding on "snow cat" tractor vehicles, kept up an intense ground search with dogs.
The search was focused on a wooded area near where Mr Dorner's pickup truck was found burning in the snow on Wednesday, and in nearby higher elevations dotted with abandoned cabins.
Search teams had followed footprints found in the snow near Mr Dorner's truck yesterday until they were lost on frozen ground.
Police have said they believe Mr Dorner was carrying multiple weapons, including an assault-style rifle, though the manifesto attributed to the suspect suggested he might be more heavily armed.
They also said they had taken steps to protect about 40 potential targets mentioned in Mr Dorner’s online manifesto.
However, the LAPD cancelled a citywide tactical alert, where officers are held over on their shifts and work overtime for as long as needed.
Mr Dorner was named as a suspect in the weekend killings of a university security officer and his fiance, college basketball coach Monica Quan, 28, in Irvine, about 64km (40 miles) south of Los Angeles.
They were found shot to death on Sunday in a car at the top of a parking structure.
Ms Quan was the daughter of a retired Los Angeles police captain who represented Mr Dorner in disciplinary action that led to his firing in 2008.
Police say Dorner was dismissed for making false statements accusing another officer of using excessive force.
Two Los Angeles police officers assigned to a search detail traded gunfire with him early on Thursday in the city of Corona, east of Los Angeles, police said.
About 20 minutes later, two other officers were ambushed and one of them was killed. They had been sitting in their patrol car at a traffic light near Corona in the town of Riverside.