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.
The three sisters and their nine children flew from Manchester to Saudi Arabia on May 28 to visit the burial place of the Prophet Muhammed in Medina.
They have not been heard from since June 9 and were due to return home on June 11.
ITV News revealed they took a flight to Istanbul a week ago. Now their family fear they may have crossed the border into Syria.
What the families would not discuss are claims a brother of the three woman is already in Syria, having fled there several months ago.
ITV News UK Editor Rohit Kachroo reports:
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.