British police arrested two more suspects Wednesday in connection with last week's bombing on a London train that injured more than 30 people.
Authorities said officers arrested a 48-year-old man and a 30-year-old man in Newport, Wales. Police had arrested another man there Tuesday night, and searches at the addresses of both arrest sites were ongoing Wednesday.
A Metropolitan Police statement did not say how the men might be linked to the bombing.
"This continues to be a fast-moving investigation," said Commander Dean Haydon, head of the Met Counter Terrorism Command. "Detectives are carrying out extensive inquiries to determine the full facts behind the attack."
A total of five men have been arrested since Friday's attack.
An 18-year-old refugee from Iraq was nabbed in the port area of Dover, a major ferry terminal for travel between Britain and France, and a 21-year-old from Syria was arrested in the west London suburb of Hounslow, which is home to London's Heathrow Airport. They remain in police custody, but neither has yet been formally charged.
A homemade bomb partially exploded at the Parsons Green station during rush hour.
Images of the bomb posted on social media appear to show a bucket on fire that had been placed inside a plastic bag close to a rail car door.
Islamic State militants claimed responsibility for the attack, but Home Secretary Rudd discounted it.
"It is inevitable that so-called Islamic State or Daesh will try to claim responsibility, but we have no evidence to suggest that yet," she told the BBC. Rudd said authorities will try to determine how the suspects may have been radicalized.
Prime Minister Theresa May said the British public may see more armed police on the streets and the transport network. The prime minister also said members of the military will begin aiding police, providing security at some sites not accessible to the public.
The blast was the fifth major terrorist attack in Britain this year.