London (CNN)British authorities have detained two more men in connection with last week's attack on the London Underground at Parsons Green station.
Two more arrests in London Tube attack inquiry
The arrests, in the city of Newport in South Wales, bring the total number of people in custody to five.
A 48-year-old man and a 30-year-old man were arrested by the Metropolitan Police Counter Terrorism Command in connection with Welsh law enforcement officials. Two addresses in Newport are being searched.
A 25-year-old man was arrested on Tuesday night in Newport.
An improvised bomb detonated on a busy train on Friday morning as it stopped at Parsons Green, injuring 30 people. It appeared to have only partially detonated.
"This continues to be a fast-moving investigation. A significant amount of activity has taken place since the attack on Friday. We now have five men in custody and searches are continuing at four addresses. Detectives are carrying out extensive inquiries to determine the full facts behind the attack," Cmdr. Dean Haydon, head of the Met's Counter Terrorism Command, said.
"We anticipate that the searches will take some days to complete and may cause further disruption. However, it is important that we continue with these searches and I'd like to thank all those affected for their support, patience and cooperation."
People who saw Tuesday's police activity in Newport said officers pounced on the suspect. Sully Ali, 19, a part-time model, told Britain's Press Association: "A big van pulled up and six officers got out and jumped this guy."
"There were two armed officers there, they didn't have their guns pointed at him but they had them on show. The guy was smiling. I didn't hear him saying anything or the police saying anything to him."
Ali said the man worked as a painter and decorator for some local residents. Residents said he had lived in the area for many years and attended local mosques, the Press Association reported.
Two men were arrested the day after the attack: An 18-year-old was detained in the port of Dover as he prepared to board a ferry service to France, and a 21-year-old was arrested in Hounslow, west London.
Police have not released the names of either of those suspects but both are believed to have been fostered by an elderly couple, Ronald and Penelope Jones, local officials told CNN on Monday.
Alison Griffiths, a Surrey County councillor, described the Joneses as "the sort of people who would never turn a child away, no matter what the circumstances."
Griffiths said the Joneses had fostered more than 280 children over the past 30 years.
They have fostered about eight refugees in the past year, including children from Afghanistan and Iraq, she added.
"This has come as a big shock to them. You don't expect it in your own house."
The couple were given medals by Queen Elizabeth II in 2010 for the continued work fostering children and young people.
ISIS has claimed involvement in the subway bombing via its Amaq News Agency.
But UK Home Secretary Amber Rudd said on Sunday afternoon: "It is inevitable that so-called Islamic State or Daesh will reach in and try and claim responsibility. We have no evidence to suggest that yet."