Three Bradford mothers and their nine children who disappeared while in Istanbul are all said to have crossed into Syria to join Islamic State (Isis).
Information that they had travelled into the war-torn country was given to the BBC by an IS smuggler. The family was reportedly split into two groups to cross the border.
The IS smuggler, operating on behalf of the extremist group on the Turkey/Syria border, said the first group travelled early on Wednesday (17 June) and the second on Thursday (18 June).
Police confirmed that at least one of the mothers had travelled from Turkey. The North East Counter Terrorism Unit (NECTU) said contact has been made with the family in the UK, suggesting "one of the missing adults may be in Syria".
Three sisters – Khadija, Sugra and Zohra Dawood – and their children, aged between 3-15 years, were reported missing on 11 June when they did not return from a pilgrimage to Saudi Arabia.
It was feared they might try to join a brother in Syria who has been fighting with IS or another extremist group after they boarded a flight from Saudi to Istanbul, a regular stopping point for those wishing to pass into Syria over the Turkish border.
The two fathers of the nine children, Akhtar Iqbal and Mohammed Shoaib, have made passionate pleas for the safe return of the women and children.
The parents of the three sisters have said they do not support their daughters' actions and were "devastated by the sudden disappearance".
In its most recent statement on the Dawood family's disappearance the NECTU, which is running the investigation alongside West Yorkshire Police, said: "We are continuing to make extensive enquiries, in order to try and ensure the safe return of everyone and to continue to offer our support to the family."