London: A UK-based Bangladeshi family of 12, including three children and two grandparents, who were on holiday in Dhaka are feared to have fled to Syria to join Islamic State terrorists.
The 12 family members have not been seen since May 17 after visiting their home country from the city of Luton, towards the north of London.
It is believed the family stopped over in Turkey on their way back to Britain before entering the war-torn country.
A statement from relatives in the UK said they were "devastated" and the disappearance was "out of character".
Bedfordshire Police said it had not confirmed whether the family had crossed the border, but inquiries were ongoing.
It has not said whether any family member was on any terror lists.
The family includes two grandparents Muhammed Abdul Mannan, 75, and his wife Minera Khatun, 53, along with three children, aged between one and 11.
According to reports, Muhammed Mannan has diabetes and his wife Minera has cancer.
The family was reported missing to police by two sons, understood to be Mannan's from a previous marriage, who also live in Luton.
Police said the family flew to Bangladesh on 10 April and flew back to Istanbul on 11 May.
They were due back at Heathrow three days later but failed to return.
In a statement, Bedfordshire Police said: "Police can confirm they are investigating the disappearance of a missing family of 12 from Luton who failed to return home from a holiday to Bangladesh."
"There is a suggestion that the family may have gone to Syria, however police have so far been unable to corroborate that information.
"Police are continuing with their enquiries and are working with relatives who are still in the UK."
Local community leader Ashuk Ahmed said he had known the family for 35 years, with Mannan going to the local mosque a number of times a day.
"The community is extremely worried about the family. There are three generations," he added.
A statement from relatives said: "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. We would urge any of them to please make contact with us or the police to let us know they are ok."