A Luton family have said that 12 missing relatives may be been tricked into travelling to Syria.
The party of 12 travelled to Bangladesh via Istanbul on April 10 and then flew back to Turkey on May 11.
They were due to fly back to Heathrow on May 14 but failed to return and were reported missing by a relative in Luton on May 17.
Police, who are working with relatives still in the UK, are now investigating the possibility that the family have travelled to Syria.
The missing members are Muhammed Abdul Mannan, 75, his wife Minera Khatun, 53, their daughter Rajia Khanom, 21, and sons Mohammed Zayd Hussain, 25, Mohammed Toufique Hussain, 19, and Mohammed Abil Kashem Saker, 31.
Mr Saker’s wife Sheida Khanam, 27, Mohammed Saleh Hussain, 26, and his wife Roshanara Begum, 24, and three children aged between one and 11 are also missing.
A statement from the family’s relatives in Luton reads: “We are devastated by the disappearance of these 12 and are very concerned for their safety.
“This is completely out of character and we are very worried of the danger they may now be in.
“Muhammed Abdul Mannan is elderly and both he and Minera Khatun have health issues.”
It adds: “This just does not make any sense. We can only think they have been tricked into going there, it is no place for elderly or young people.
“We would urge any of them to please make contact with us or the police to let us know they are ok.”
Anyone with any information about the 12 is urged to call police on 101.