Police at Heathrow Airport in London have arrested a 19-year-old man suspected of terror offences, the Met said on Sunday.
He was detained by counter-terror SO15 officers on suspicion of "preparing for acts of terrorism," reported the BBC. A spokesman said the arrest was "Syria-related."
The force said it had searched an address in Camden, north London, but that the arrest was "not in response to any immediate risk or threat."
The teenager is being held in custody at a south London police station, according to the BBC.
In a separate incident at the airport, the Met said officers from the same unit arrested a 20-year-old who they believe sent "money/property overseas for the purposes of assisting terrorism in Syria."
The British national was arrested as he entered the UK and is also being detained in south London.
Both suspects were held under the Terrorism Act 2006.
Western powers have expressed concern that some of their citizens have traveled to fight in the civil war in Syria, some of them joining extremist groups that might one day seek to strike their home countries.
Recently published statistics say that over 75,000 foreign nationals have been fighting in the Syrian civil war. While the majority are from Muslim countries, there are also Russians, Germans, Canadians, British and French citizens taking part in the fighting.
In January, 26 year-old Nawal Msaad was apprehended in Heathrow Airport as she tried to smuggle 20,000 euros ($27,364) to rebel forces.
Several months ago, Britain began revoking the citizenship of its nationals who join the Syrian civil war.