Local law enforcement agencies investigate several thousand cases of missing people each year and most turn out to be runaway teens.

Whether it's a teen girl rebelling against her parents and sneaking away to a friend's beach house or a serious attempt at leaving the area, most of the missing persons cases involve teens leaving of their own accord.

The Kern County Sheriff's Department investigated 1,916 missing persons reports in 2006, with 147 in which the person was considered to be in danger.

"In a standard missing persons case, there is no evidence of foul play or that the missing person is in danger," sheriff's Sgt. Ed Komin said. "Juveniles in that category often have a history of running away."

But some cases are different.

In a recent incident, a 16-year-old girl didn't return home from school Nov. 9 and her mother received a phone call saying the girl would be harmed.

In another, a woman disappeared after arguing with her boyfriend on Nov. 2 and relatives heard from someone saying the boyfriend had threatened to hurt her.

In the two recent cases, both women were considered at risk because of the circumstances of their disappearance.

In the first case, 16-year-old Clarisa Martinez didn't return home and her mother received the threatening phone call. It turns out the teen spent the weekend at a friend's house on Mount Vernon Avenue and was found by police shortly after midnight Monday.

Relatives have said they don't know why Martinez didn't answer the phone all weekend. Bakersfield police Sgt. Greg Terry said detectives are looking into the source of the phone call to the mother. When Martinez went missing, detectives and patrolmen searched for her.

In the other case, Maria Esther Jauregui, 51, went missing after arguing with her boyfriend. A sheriff's deputy found her body in an SUV three days later in the 6000 block of Fairfax Road. Terry said detectives and patrolmen searched and checked numerous locations.

The boyfriend, Francisco Najera, has been named a suspect in the case and has not been found.

In both cases, the media was alerted when the women first went missing because both were potentially in immediate danger.

The Bakersfield Police Department and Kern County Sheriff's Department categorize missing persons reports by the danger to the person missing. A person doesn't have to be missing 24 hours before detectives start searching. That's only something you see on TV, Terry said.

Sometimes there are cases of adults going missing for weeks at a time and it turns out they were on vacation or just left without telling anyone. Detectives write a report and go to places where the missing person might be, Komin said.

Cases of adults who intentionally go missing are rare, Terry said.

The missing person's name is entered into a national database within four hours and search efforts are exhausted in locating someone who is considered at risk, Terry said.

"If we get a call from someone saying their 3-year-old was playing in the front yard and is now gone, there's no limit to what we do," Komin said.

Those resources include search-and-rescue units, helicopters and alerting all area law agencies as soon as possible. But that kind of case doesn't happen often, Komin said

Cases also sometimes change. A standard missing person case can become a critical one if new evidence indicates the person was a victim of foul play. After 30 days, a standard missing person case is elevated to a critical missing person case, Komin said.