A mother feared to have been planning to travel to Syria with her four children has been arrested after returning to Britain.
Zahera Tariq, 33, was held on suspicion of child abduction at Luton Airport on Thursday night.
The children - aged between four and 12 - have been taken into police protection, Scotland Yard said.
Tariq was detained in Turkey on Tuesday after the family went missing from their home in Walthamstow, north-east London, last week.
They were believed to have flown from London City Airport to Amsterdam on August 25. All of the children were said to be "safe and well" when the group was detained by Turkish authorities.
Confirming the latest development, a Metropolitan Police spokesman said: "Officers from the Met's Counter Terrorism Command (SO15) have today arrested a 33-year-old woman at Luton Airport on suspicion of child abduction.
"The woman was arrested at approximately 7.45pm as she was entering the UK, having just disembarked a flight from Istanbul, Turkey.
"Her four children, with whom she was travelling, were taken into police protection. Inquiries continue."
Several cases have emerged in which women and children from the UK are feared to have gone to parts of Syria controlled by the so-called Islamic State.
Scotland Yard recently disclosed that it believed more than 40 women and girls had travelled to Syria from Britain in the last year.