Ben Wallace, the security minister, told the BBCâs âTodayâ radio program that the homemade device used in the attack had contained triacetone triperoxide, or TATP, an explosive similar to the one used in the Manchester Arena bombing in May.
The Metropolitan Police said a major hunt was still underway for any other suspects connected to the subway bombing. The police in Kent warned residents in a statement on Twitter to expect more officers and âmilitary personnelâ on the streets. Hundreds of soldiers have been deployed across strategic sites, the Metropolitan Police said.
Dover, about 75 miles from London, is one of the main ports on the English Channel for ferry services linking Britain with mainland Europe.
As part of the bombing investigation, armed officers on Saturday were searching at least one house in Sunbury-on-Thames, on the outskirts of the capital and about three miles from Heathrow Airport in London, according to The Associated Press, the BBC and other local news outlets.
The police confirmed that a residential address in the area had been evacuated and was being searched, but declined to say if the operation was linked to the suspect arrested.
Sunbury is 10 miles west of Parsons Green, where the explosion occurred. Residents reached by phone on Saturday said that shortly before 2 p.m., police officers arrived to seal off the residential neighborhood around Cavendish Road and Burgoyne Road.
Louise Margetts, 54, said she was returning from the supermarket to her home when she saw four police vehicles, including a police canine unit, speeding up the road.
âThe officers at the back jumped out and started cordoning off the road,â she said. âThey were running, and said, âTurn around now.ââ
Mrs. Margetts, a teacher, managed to get home but the police arrived at her door soon afterward.
âThey didnât really tell us anything,â she said. âThey knocked, well, hammered, on the door and said: âOut now. We canât say why.ââ
After the police sealed off the surrounding streets, residents were told that they had to evacuate and some were offered transport to a local rugby club, some residents said. Others were allowed to go to relatives nearby.
Barry Sutton, 53, said he saw several Surrey police vehicles on the edge of the cordon.
âThe police are going house to house behind the tape, evacuating people,â he said by phone. âThere was no sense of panic, but there were a lot of police; it was a proper operation.â
Sunbury is very close to Londonâs outermost boroughs and is served by commuter trains, but is not on the London Underground network.
Police officers have been combing the footage from CCTV on the London transportation network for clues about who had placed the bomb that exploded on Friday.
The crude explosive, wrapped in a plastic grocery bag that was concealed in a bucket, exploded at 8:20 a.m., during the morning rush on a train at the station in West London.
The whole carriage was engulfed in flames, witnesses said, and dozens of passengers trampled over one another to try to exit the train. No one was killed in the attack, but several people were hospitalized for injuries including burns and fractures.
The terrorist attack was the fifth major assault in Britain in less than six months, and the first to hit mass transit since the deadly bombings of 2005 that killed 52 people. While Londoners expressed relief that no one was killed in Fridayâs blast, the episode renewed fears about the threat of terror.
âThis has become the new normal,â said Harry Walker, a Parsons Green resident. âWe get attacked, and then we carry on, waiting in anticipation for the next one.â
âThe fact that they struck Parsons Green,â he added, âwhich is way out from the center, is them giving a very clear message: âWe can do it anywhere at any time.â â
The Parsons Green station reopened on Saturday, less than 24 hours after the attack, but Mr. Basu urged the public to âremain vigilant.â