Contact has been made by one of three British sisters missing with their nine children - and they may have already entered Syria.
Sisters Khadija Dawood, Sugra Dawood and Zohra Dawood are thought to have taken the nine - aged between three and 15 - to the war-torn country to join Islamist militants.
West Yorkshire Police said: "We have received information that contact has been made with the family in the UK which suggests one of the missing adults may be in Syria.
"Contact has been made by one of the missing women and there is an indication that they may have already crossed the border into Syria but this is uncorroborated."
The revelation comes a day after the husbands of two of the sisters begged their families to come home in a news conference.
Akhtar Iqbal and Mohammed Shoaib broke down as they pleaded desperately for the group to return so they can get back to their "normal lives".
Assistant Chief Constable Russ Foster said: "We are extremely concerned for the safety of this family ... We would urge anyone with information about the family's whereabouts to come forward and speak to police so the family can safely return to the UK.
"Anyone with information should call West Yorkshire Police on 101.
"Any piece of information, no matter how small, could help the UK or overseas authorities to locate the family so that they can be safely returned home to their loved ones.
"Police have been working with the extended Dawood family and the Turkish authorities since they were reported missing in an attempt to locate the family and return them to their loved ones."
The missing group, all from Bradford, went on an Islamic pilgrimage to Saudi Arabia on 28 May.
But instead of returning to the UK, they flew on 9 June from Medina to Istanbul in Turkey - a commonly used route into Syria.
At that point they effectively disappeared and their mobile phones were switched off.
It is believed the sisters have a relative fighting in Syria.
In his appeal on Tuesday, Mr Iqbal, Sugra's husband, said: "I miss you, and love you. I cannot live without you.
"Please, please call me so I know you are safe, especially my three-year-old son Ismaeel."
Mr Shoaib told his wife Khadija: "We had a perfect relationship, we had a lovely family. Please contact me whenever you want. Please come back."
Zohra Dawood's husband was not at the news conference as he is currently not living in the UK.
Among the youngsters are Khadija's children, Maryam Siddiqui, seven, and five-year-old Muhammad Haseeb.
Sugra's children Junaid Ahmed Iqbal, 15, Ibrahim Iqbal, 14, Zaynab Iqbal, eight, Mariya Iqbal, five, and three-year-old Ismaeel Iqbal have also disappeared.
Zohra's missing children are Haafiyah Binte Zubair, eight, and five-year-old Nurah Binte Zubair.
