Two Britons arrested at Heathrow Airport over terrorism allegations will be questioned about the kidnapping of a British photographer in Syria.
The man and woman, both 26, were held at 8.30pm on Tuesday after arriving in the UK on a flight from Egypt.
They were arrested on suspicion of travelling to Syria to support terrorist activities.
Scotland Yard confirmed that one line of inquiry was whether the pair were involved in the abduction in the war-torn Middle Eastern country.
Photographer John Cantlie, who had worked for the Sunday Times, and Dutchman Jeroen Oerlemans were both held for a week.
Mr Cantlie later said that one of his captors had claimed to be an NHS doctor.
Searches were being carried out at two residential addresses in east London, the Metropolitan Police said.
Counter-terrorism officers arrested the pair on suspicion of the commission, preparation or instigation of acts of terrorism and they remain in custody at a central London police station.
The arrests are part of an investigation into travel to Syria in support of alleged terrorist activity. In recent months concerns have been raised that foreign nationals are travelling there with the intention of supporting jihadist movements.
In August, Khalid Mahmood, Labour MP for Birmingham Perry Barr, told the BBC that a number of people in his constituency were travelling to the war-torn Middle Eastern state, and that he expected this to increase.