The Bradford sisters missing with their nine children were stopped from leaving the UK in March, ITV News has learned.
Their trip to Saudi Arabia was rebooked for May but there is no suggestion they were intending to travel to Syria at that time. Police are now trying to work out when the trip was planned.
A Bradford family have appealed for help to trace three British sisters who are feared to have travelled to Syria with their children.
Khadija Dawood, 30; Sugra Dawood, 34 and Zohra Dawood, 33, and their nine children, aged between three and 15, travelled to Saudia Arabia on May 28 for an Islamic pilgrimage.
The children have been named as Ismaeel Iqbal, 3; Muhammad Haseeb, Mariya Iqbal and Nurah Zubair, all aged 5, Maryam Siddiqui, 7; Zaynab Iqbal and Haafiayah Zubair, both aged 8; Ibrahim Iqbal, 14 and Junaid Ahmed Iqbal, 15.
The family, from Bradford, failed to return to the UK on June 11, according to solicitors acting for the Dawood family.
It's believed ten members of the group boarded a flight from Madina, Saudia Arabia to Istanbul on June 9.
No details were found for two of the children - Haafiyah Zubair and Nurah Zubair - having boarded the flight.
Speaking from Pakistan, one of the husbands of the missing Bradford thought to be heading to Syria has told ITV News of his worry.
Here's what we know about the Bradford family of 12 who are feared to be travelling to Syria.