Yahyah Farroukh, 21, is listed as living at an address in Stanwell, Surrey, which was
searched by officers on Sunday.
He was arrested at a fried chicken shop where he worked in Hounslow, west London, on Saturday night.
Another 18-year-old was
detained at Dover ferry port on Saturday morning.
The younger man is suspected of planting the device, which exploded on a District Line train in London on Friday morning, injuring 30 people.
Leader of Spelthorne Borough Council Ian Harvey, whose ward is Sunbury East, said the 18-year-old suspect is understood to be an Iraqi orphan who moved to Britain when he was 15.
Mr Harvey said: "One thing I understand is that he (the 18-year-old) was an Iraqi refugee who came here aged 15 - his parents died in Iraq."
Police said the two men are being questioned on suspicion of offences under the Terrorism Act.
Farroukh is originally from Damascus, according to his Facebook profile.
West Thames College, where he said he studied English, confirmed he was a student between 2013 and 2015.
Suleman Sarwar, 43, who owns Aladdin's Fried Chicken on Kingsley Road, Hounslow, with his brothers, said Farroukh was arrested outside the takeaway after his shift finished at 11.30pm on Saturday.