Two more people have been arrested in connection to the Parsons Green terror attack, bringing the total to five.
A 48-year-old man and a 30-year-old man were arrested under section 41 of the Terrorism Act following a police raid on an address in Newport, in south Wales, on 20 September.
This follows the arrest of a 25-year-old man at another address in Newport on the evening of 19 September. Officers are still searching both sites as part of the ongoing investigation.
Several people were injured by the explosion and subsequent stampede on a District Line train in West London, which occurred at around 8.20am on 15 September.
Police confirmed they are treating the explosion, caused by the "detonation of an improvised explosive device", as a terrorist incident.
Two suspects were previously arrested by police during their investigation; an 18-year-old man was apprehended in the port area of Dover, and a 21-year-old man was arrested in Hounslow. A warrant for both suspects' further detention has been granted by Westminster Magistrates' Court.
Commander Dean Haydon, head of the Met Counter Terrorism Command, said: "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.
"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.
"As police and our partners do all we can to confront the threat, public vigilance remains as vital as ever. We urge the public to report any suspicious activity to the police by calling us, in confidence, on 0800 789 321, or in an emergency by dialling 999.
"We are asking the public to look out for anything that seems out of place, unusual or just doesn't seem to fit in with day-to-day life. It may be nothing, but if you see or hear anything that could be terrorist-related trust your instincts, then act, and call us."