All four women dissappeared along a half-mile stretch of First Street between Grand Avenue and the 55 Freeway.
The area where the women disappeared from is known for prostitution and drugs. Police say some of the women have substance abuse issues and or have been arrested for prostitution in the past.
Investigators say they do not know if the disappearances are related or if the women are victims of foul play, but family members fear the worst.
Many of them have posted fliers of their missing loved ones in hopes of tracking them down.
Kianna Jackson, 20, was the first to disappear on Oct. 15. Two weeks later, Josephine Vargas, 34, vanished.
On Nov. 12, Martha Anaya, 28, disappeared. Lastly, Andrea Nichole Palma vanished on Nov. 23.
Missing-person reports were filed by family members of the women.
Family members fear that the women may have been kidnapped for human trafficking. They say other women in the area have told them that several suspects have tried to grab them.
While police do not know if the cases are connected, they say it certainly is suspicious that four women have disappeared from the same area.
"If they're related, we'd certainly like to know," said Santa Ana Police Cpl. Anthony Bertagna. "And if there is a problem and somebody is taking these people then we want to know, we want to catch them and we want to get these people back to their families."
Family members say they are praying that all four women are found safe and sound.
"I'm just scared, it's been going on - four girls gone already, and my girlfriend was the third one to be missing," said Jessie Fisher, the boyfriend of one of the missing women. "A week right after that, a week and-a-half, another girl went missing too, and I'm just like what's going on here, you know?"
Anaya's family says the 28-year-old would never have left her two daughters.
"I know my mother, said Melody Anaya, the missing woman's daughter. "I know she would never just leave, she takes my sister to school everyday, it's not like her to go missing."
Priscilla, Josephine Vargas' mother, says she just wants her daughter home.
"I don't know if they took her out of state or what," said Priscilla, "all I want is my daughter back, it's all I ask."
Police say they have entered the four women in the National Missing and Unidentified Persons System and have also been checking jails, hospitals and morgues for any signs of them.
So far, investigators have found no clues.
The investigation is ongoing. Anyone with information was urged to contact OC Crime Stoppers at (855) 847-6227.