An international search is underway for a family of three sisters and their nine children who have fled Bradford and are suspected to be travelling to Syria via Turkey.
On Wednesday, West Yorkshire police said in a statement that one of the missing women has made contact with her family in the UK and authorities now fear she may already have crossed the border into Syria, although that is yet to be confirmed.
"We are extremely concerned for the safety of this family, especially the nine children aged between 3-15 years.," said ACC Russ Foster.
Foster went on to say that due to the current unrest in Syria and the increasing dominance of ISIS in the war-torn country, anyone travelling there will automatically raise concerns from the authorities.
"We are concerned about anyone who has or is intending to travel to the part of Syria that is controlled by the terrorist group calling themselves Islamic State. It is an extremely dangerous place and not a place where young children should be taken," he said.
"The choice of returning home from Syria is often taken away from those under the control of Islamic State, leaving families in the UK devastated and with very few options to secure their loved ones safe return," he added.
The family, who are aged between 3 and 34 and are all from Bradford, West Yorkshire, made a pilgrimage to Medina in Saudi Arabia on 28 May.
Then at least 10 of the group are reported to have boarded a flight to Turkey on 9 June instead of flying back to Manchester as planned.
The Guardian reported that police were monitoring the family after a brother of the sisters travelled to Syria two years ago, according to Alyas Karmani, a local councillor.
West Yorkshire police said on Monday night that they were "working extensively with overseas authorities" to find the family.
"We are extremely concerned for the safety of the family and would urge anyone with information to come forward and speak to us," said assistant chief constable Russ Foster.
"Our priority is for their safe return; their families are gravely worried about them and want them home. One of our primary concerns is the safety and welfare of the young children."
The women include Sugra Dawood, 34, who has five children.
Zohra Dawood, 33, who has two children.
And 30-year-old mother of two Khadiga Dawood.
Lawyers acting for the three women's husbands, who did not travel and are said to be "worried out of their minds", criticised the police response so far.
Solicitor Bilaal Khan told The Guardian: "They have grave concerns because the matter was reported on the 11th.
"Obviously today we're on the 16th and we've had no answers. Unfortunately the information that we have about them travelling to Medina [in Saudi Arabia] were all done by family members. In fact, everything they've done is all off their own backs and it's quite sad really."
"We've been informed that there's only one [police] officer [in Turkey] so what West Yorkshire police have to do is contact the Met police, who then contact the officer in Turkey, who I'm told is inundated with loads of inquiries and we were told that the officer doesn't have enough time."
Bradford West MP, Naz Shah, spoke to the fathers and told the BBC that the disappearence came as a shock.
"I asked them if there was any indication and they said absolutely not – it was a shock to them, it came out of the blue," she said.
"At this time there is no contact, absolutely zero contact with the women or children. The last contact was a few days ago when they were due to leave."