Francisco "Franc" Cano, 27, and Steven Dean Gordon, 45, are accused of raping and killing four women in Orange County, and investigators suspect there is at least one other victim.
The missing person is described as a black woman in her 20s, petite stature, with black hair and numerous tattoos on her body. Police say she may have ties to the city of Compton.
The woman was last seen between Feb. 14 and Feb. 16 near Katella and Orangewood avenues or Beach Boulevard north of Katella Avenue.
"She likely checked into a local motel and did not check out, leaving behind her belongings," Anaheim police said in a statement.
The bodies of three of the victims -- Kianna Jackson, 20, Josephine Vargas, 34, and Martha Anaya, 28 -- have not been found. All three women had mysteriously disappeared last fall in Santa Ana.
Detectives got a break in the case when the body of 21-year-old Jarrae Nykkole Estepp was discovered at an Anaheim trash recycling center on March 14.
Anyone with information about the possible fifth victim is urged to call Orange County Crime Stoppers at (855) TIP-OCCS.