Police have arrested a second man at Heathrow airport in connection with involvement in terrorist activity in Syria.
The 20-year-old British national has been detained under suspicion of sending money for the purposes of assisting in terrorism in Syria.
The latest report comes after a 19-year-old was arrested at Heathrow airport by counter terrorism officers this afternoon as he attempted to board a plane, after it was suspected that he was travelling to Syria to take part in the insurgency.
The teenager, who is not understood to be British, was arrested before he boarded the aircraft. Officers have searched a flat in Camden, London, as part of the investigation.
A spokesman for Scotland Yard said: "Officers from the MPS Counter Terrorism Command, SO15, have today arrested a 19 year-old man at Heathrow on suspicion of preparing for acts of terrorism (Terrorism Act 2006).
"'Officers have searched an address in Camden. The arrested man remains in custody at a police station in south London. Enquiries continue."
The arrests are not believed to be connected and the men are being held in separate South London police stations where they are being questioned by anti terrorism officers.
A Metropolitan Police spokesperson said: "Investigations are ongoing at present. The two arrests are not being linked at the moment."
Flights have not been affected by the incident and the airport remains open.
Earlier this month, a Muslim man became the first Briton to be found guilty of travelling to Syria to fight in the civil war.
Police said the conviction of Mashudur Choudhury, 31, was likely to pave the way for others returning from the fighting to be prosecuted.
It is believed around 400 Britons have gone to the war-torn country to wage war in the past two years.