LONDON , Feb. 20 (UPI) -- The three missing schoolgirls from London who police believe are headed to Islamic State-controlled territory have been smuggled into Syria.
The Metropolitan Police believe they were smuggled near Turkey's Kilis border crossing on Friday or Saturday.
London police appealed for public help to locate three teenage girls on Friday.
Shamima Begum, 15, Amira Abase, 15, and Kadiza Sultana, 16, pupils at London's Bethnal Green Academy, flew from England to Istanbul on Feb. 17, and authorities feared they may be attempting to reach Islamic State territory in Syria. They told their parents they were going out for the day.
A fourth girl, a friend of the three, left London for Syria in December.
Richard Walton of the London Metropolitan Police Counter Terrorism Command said there is concern in Britain over the number of young women eager to go to Syria to involve themselves in IS. He referred to the three as "extremely vulnerable."
Police released a photo of the missing girls, taken in London's Gatwick Airport, and issued a statement saying, in part, "Any piece of information, no matter how small, could help the U.K. or Turkish authorities locate them so they can be safely returned home to the U.K."
The incident is part of a trend in which young women head for the Middle East to help IS. Three Colorado girls were intercepted in Germany as they attempted to go to Syria in October, and another Coloradan, Shannon Maureen Conley, 19, was arrested in Denver's airport before she could leave to allegedly marry an IS member she met online. Conley received a four-year prison sentence in January after admitting she sought to participate in IS activities.
Meanwhile, South Korean officials confirmed Tuesday that an 18-year-old man who went missing from Turkey has joined IS.