Renu Begum, eldest sister of Shamima Begum, holds her sister’s photo as she is interviewed by the media at New Scotland Yard. The U.K. revoked Shamima Begum’s British citizenship two years ago, citing security concerns.

LONDON, ENGLAND – FEBRUARY 22: (EDITORS NOTE: FACE IN PHOTO BEING HELD DELIBERATELY COVERED BY SISTER) Renu Begum, eldest sister of Shamima Begum, 15, holds her sister’s photo as she is interviewed by the media at New Scotland Yard, as the relatives of three missing schoolgirls believed to have fled to Syria to join Islamic State have pleaded for them to return home, on February 22, 2015 in London, England. Police are urgently trying to trace Shamima Begum, 15, Kadiza Sultana, 16, and 15-year-old Amira Abase after they flew to Istanbul in Turkey from Gatwick Airport on Tuesday. (Photo by Laura Lean – WPA Pool/Getty Images)