Police searching for missing twin teenage girls from Greater Manchester believe the pair are now in Syria.
The 16-year-old girls were reported missing from their home on 26 June and are believed to have first travelled to Turkey from Manchester Airport.
The North West Counter Terrorism Unit is now investigating the reason for travel and whether they were assisted.
Det Ch Supt Tony Mole said the welfare of the girls “is our overarching priority”.
He said: “At this stage we don’t know for sure why they are there or exactly who they are with.
“They are clearly posing a threat to themselves and potentially the community and their family and friends are concerned for their well-being.”
Some 6.5m people have been displaced in Syria since an uprising against President Bashar al-Assad began in March 2011.
About 500 UK Muslims are thought to have gone to fight in Syria.
However, more than 100 imams in the UK have appealed to British Muslims not to travel to Syria and Iraq.
In an open letter they said they had come together as a unified voice, to urge people not to fall prey to sectarian divisions or social discord.