An 18-year-old woman was arrested on suspicion of terrorism offences at Stansted Airport.
Counter-terrorism officers arrested the teenager when she arrived on a flight at around 4pm on Friday (January 16), Scotland Yard said.
She was taken to a central London police station and has since been bailed until mid-February.
The woman was arrested on suspicion of preparation of terrorist acts and membership of a proscribed organisation, police said.
As part of the investigation a 21-year-old man was arrested in Hackney on Wednesday, October 29 on suspicion of assisting another to commit acts of terrorism, or to engage in any conduct for the committing of such acts, by facilitating another to travel abroad.
He was taken to a south London police station, where he was later bailed to return to on a date in late December.
He has since been re-bailed to a date in January.
A search at the residential address in Hackney was also carried out.
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