The body of Lidia Castillo, 45, was found around 9 p.m. Sunday on the 2500 block of East Avenue I.
Los Angeles County Sheriff's detectives say Castillo had been living at the mobile home with her boyfriend, who they have not identified.
Family members went to Castillo's home Sunday night since she had not been heard from since last Wednesday. They found her dead in her bedroom, but it's unclear if foul play was involved. The coroner's office will perform an autopsy to determine the victim's cause of death.
"To find out that there was a lady that they found her body in a mobile home on this back street, that's too close for comfort. I live here. It's just too much," said Lancaster resident James Anderson.
Investigators say the victim's mobile home was ransacked and items were missing.
Castillo's boyfriend is a person of interest in the case, and authorities want to talk to him. Investigators believe he took Castillo's red 2007 four-door Chevy Impala with Nevada license plate 805 YBH.
Residents in the area say the woman moved into the mobile home park less than a month ago.
"It's crazy. We've never had anything like that happen in this neighborhood," said Cesar Bustos. "It's always been a safe neighborhood for me. It's kind of shocking to me."
"We live right down the street right here, and it's just devastating living here in Lancaster," said Diane Carter. "Every week we hear something about Lancaster on the news, and it's devastating. It's really scary."
Anyone with information was asked to contact Los Angeles County Crime Stoppers at 1-800-222-TIPS.