By Kristen Johanson

PHILADELPHIA (CBS) — Nearly 300 children have been reported missing in Philadelphia so far this year, but only one Amber Alert has been activated in the state.

With increased awareness of human trafficking, Philadelphia Police are reviewing their missing persons policy.

15-year-old Kayla Bryant, missing since June 30th.

15-year-old Daisha Miller, July 14th.

Arianna Tirado, 13. She vanished this past weekend.

That’s just three of the 278 children reported missing in Philly this year.

“Each case is going to be a little bit different,” said Pennsylvania State Police Corporal Adam Reed.

He says local cops must satisfy several dozen requirements before they request the state issue an Amber Alert.

“These factors could include descriptive information and the timelines in the report,” said Reed.

Troopers work with National Center for Missing and Exploited Children, where a case worker tracks the investigation of each child.

“The system isn’t really for runaways or for kids perhaps that voluntarily left,” Reed said.

Philly detectives are reviewing and updating their missing persons policy to work alongside the city’s recently formed human trafficking task force.