Police are searching the family home of one of nine Britons who allegedly tried to cross illegally into Syria.
Officers are at the home of Labour councillor Shakil Ahmed, whose son Waheed is among a group of five adults and four children being held in Turkey.
The Rochdale councillor said he had thought his son was on holiday.
The Foreign Office are providing consular assistance to the British nationals but cannot confirm when they will be deported back to the UK.
Waheed’s aunt, Zadia Bi, two of her sons and one of their wives, were the other adults detained, Mr Ahmed said.
The group from Rochdale, which also included children aged one, three, eight and 11, was seized in Hatay near the Syrian border on Wednesday.
In a statement, Mr Ahmed said he wanted his son to come home “as soon as possible so I can find out what’s going on”.
“My son is a good Muslim and his loyalties belong to Britain, so I don’t understand what he’s doing there,” he said.
“If I thought for a second that he was in danger of being radicalised, I would have reported him to the authorities.
“He’s studying a degree in politics and sociology at Manchester University and has a good future ahead of him.”
The councillor also said that he thought his son was in Birmingham on a work placement.
Speaking to the Daily Mail, he added: “All I know is that they were on holiday and then the next thing I am told is that they have been arrested.”
Greater Manchester Police and the North West Counter Terrorism force have launched an investigation to establish why the group apparently tried to enter Syria.
All nine would be sent back to the UK “in due course”, police said.
‘No sense of belonging’
Assistant Chief Constable Ian Wiggett said: “What is obviously concerning is why a family were seemingly attempting to take very young and vulnerable children into a war zone; such a volatile and dangerous environment is no place for them whatsoever.”
He said the primary concern was the “safety and welfare” of the children, and efforts were being made to ensure a “full safeguarding strategy” was in place upon their return.
Officers had uncovered “no evidence whatsoever” of any imminent threat to the UK that was linked to the group, police added.
Usman Nawaz, 25, who was part of the last Labour government’s Young Muslims Advisory Group and attended the same school as Waheed Ahmed, told BBC Radio 4’s Today programme that some young British Muslims do not feel a sense of belonging.
He said: “For some it probably is an adventure but for others they think they are doing something noble so it’s the narrative that’s being presented to them.”
Dalaat Ali, a family friend of Shakil Ahmed told BBC Radio 5 live Mr Ahmed was in a state of shock: “I spent the day with him yesterday.
“He told me, ‘I’m a councillor and we’re supposed to be leading on things like this and this happens in my own house and I don’t know anything about it.'”
Mr Ali, who is also a councillor in the same Kingsway ward as Mr Ahmed, said it was time for a wake-up call for the wider community: “There’s been many wake-up calls before but we have to be assertive and work together with all communities, all sections and with children.”