(CNN) -- A manhunt for a serial killer is under way in Southern California after the fatal stabbings of three homeless men, authorities said.
In a span of 10 days last month, three transient men were killed in Anaheim, Brea and Placentia, according to police.
"Each victim was stabbed multiple times," said Sgt. Bob Dunn of the Anaheim Police Department.
Investigators believe it's the same assailant, he said, and urged the homeless to stay in groups, and avoid sleeping in dark and secluded areas.
"There are some additional similarities between the victims that we are not going to discuss," he said.
Dunn declined to comment on the weapon or other leads connecting the three attacks.
The first victim, a 53-year-old male, was stabbed on December 20 in Placentia. Eight days later, a 42-year-old was found fatally stabbed on a riverbed trail in Anaheim. A third victim, a 57-year-old, was found on December 30 in Yorba Linda.
Police released a surveillance camera photo of the suspect taken on December 20. It shows the suspect standing a few feet away from the victim, who appears to be lying on the ground next to a strip mall, according to police.
Authorities have set up a task force to probe the killings comprising of the FBI and the Orange County Sheriff's Department.
Anyone with information is asked to call 714-765-1944.