Urban legend has it that people often go missing in San Francisco.

Based on police records, this purported myth doesn't entirely come out of thin air.

The San Francisco Police Department's Missing Persons Unit keeps track of individuals who mysteriously vanish in the city. There are currently 988 open cases going back as far as 1976, according to Sgt. Andrea Creed, one of two investigators within the unit.

"I believe we do have a lot of people who go missing here," Creed said.

Most of the open cases involve adult males; only 23 percent are juveniles and 36 percent are female.

"We get a significant number of cases where people tell their family, 'I'm going to San Francisco,' so those cases end up getting reported to us because that's the only link the family has," Creed said. "We also get a significant number of people who come to San Francisco because of the draw to the Golden Gate Bridge."

The city saw its highest levels of disappearances in the 2000s, she said, when it became mandated to include individuals who are temporarily unaccounted for at places such as group homes for juveniles, drug treatment centers and halfway houses.

The National Child Search Assistance Act requires each federal, state and local law enforcement agency to enter information about missing minors into the FBI's National Crime Information Center database within two hours of them being reported missing.

Creed said her office gets a lot of false alarms because each time a person leaves a program facility without notice, it gets reported as a missing person to police, even though the majority return within a few hours, she said.

"I believe the numbers are slightly skewed," Creed said. "The numbers have gone up over the years because of the way reporting happens now."

Creed said police are unable to provide specific details regarding individual cases that are still open.

Cases of persons reported missing and found relatively quickly are cleared right away and not tracked in the online system, according to Sgt. Michael Andraychak.

After a person has been reported missing, officers often investigate their whereabouts by doing well-being checks or calling local hospitals to search for any unidentified patients, Andraychak said.

"When we have someone at risk, that makes it a mandatory continuing search," Andraychak said. "It's not just that we take a report and file it — there's a lot of work we do."

At-risk missing persons include children under the age of 12 and seniors over the age of 75, where dementia could be a concern. If a missing person is not at at risk, the case gets reviewed by a station lieutenant after 30 days and before being forwarded to the Missing Persons Unit.

Since the SFPD began using its current online tracking system in 2016, there have been 4,930 missing person cases, of which 45 percent were female, 34 percent were minors and 6 percent were seniors, according to Andraychak.