Go Inside the Bus Station the ISIS-Bound Schoolgirls Passed Through

— -- Surveillance video released Sunday shows the three British teens who reportedly traveled to Syria last month to join ISIS.

Shamima Begum, 15, Amira Abase, 15, and Kadiza Sultana, 16, were last seen February 17 when they boarded a flight from London's Gatwick airport headed for Turkey.

The surveillance video obtained by the BBC shows the girls waiting in a bus station for around 18 hours. They then boarded a bus to Gaziantep, a Turkish border town that has gained notoriety for being portal for foreign fighters travelling to Syria.

ABC News’Chief Global Affairs Correspondent Martha Raddatz visited the bus station in Istanbul. Watch the digital original video above to learn more.