Detectives have been given a further six days to question three men arrested over the 7 July London bombings.
Fifty-two people were killed in four explosions on 7 July 2005
Taxi driver Mohammed Shakil, 30, from Leeds, was arrested on Thursday at Manchester Airport with a 23-year-old named by BBC sources as Shipon Ullah.
A third man, later named as Sadeer Saleem, 26, was arrested in Leeds.
All three are being held at Paddington Green police station in London. Suicide attackers killed 52 people on three London trains and a bus in 2005.
Detectives have been searching five houses in the Beeston area of Leeds, and two premises in east London.
The three men, arrested on Thursday, are being interviewed by anti-terrorism officers.
They are being held on suspicion of the commission, preparation, or instigation of acts of terrorism.
Under anti-terror laws, police can hold them for a maximum of 28 days.
Warrants to detain all three men for a
further six days were granted at the City of Westminster Magistrates Court in London.
Abdul Waheed, owner of Gee Gee Cars in Beeston Park, said Mohammed Shakil had worked for his firm for the past four months.
But two weeks ago father-of-the-three Mr Shakil handed in his notice, saying he was going to Pakistan.
On Thursday, he and Shipon Ullah took a taxi to Manchester Airport intending to fly to Pakistan. But they were arrested before they could board the plane.
"He said he would maybe stay over there for three or four months," said Mr Waheed.
"I said he was most welcome back here when he got back."
But Mr Waheed noticed soon after that Mohammed Shakil's house, in the Beeston area of Leeds, had been sealed off by police.
"He is so polite - a good, hard worker and well-educated. He never had a problem with customers. I'm very shocked."
Mohammad Sidique Khan, 30, Shehzad Tanweer, 22, and Germaine Lindsay, 19, detonated bombs on three Tube trains and Hasib Hussain, 18, attacked a bus.
The searches are expected to take some time
The four bombers died in the explosions, and no-one has yet been charged over the attacks.
Scotland Yard said the arrests were part of a pre-planned, intelligence-led operation and also involved the West Yorkshire Police Counter Terrorism Unit.
Ch Supt Mark Milsom, of West Yorkshire Police, said it would likely be a matter of days before searches of the addresses in Beeston were complete.
"People are anxious and waiting to see what happens. If things do happen we will let them know if we can.
"We've always been very open about what is happening and that's what we will continue to be."
The houses being searched in Leeds are in Cardinal Road, Colwyn Road, Firth Mount, Tempest Road, and Rowland Place.
Tanweer and Hussain were both living in Beeston when the attacks were carried out, and Khan grew up in Beeston. Tanweer lived in Colwyn Road with his parents.