A teenager has been arrested by detectives investigating the Parsons Green terrorist attack, bringing the number of people being held to six.
The 17-year-old boy was detained after officers executed a warrant at an address in Thornton Heath, south London, at around 12.05am on Thursday.
All six remain in custody at a south London police station, Scotland Yard said.
Meanwhile officers have begun a search of the property where the teenager was arrested under section 41 of the Terrorism Act.
Commander Dean Haydon, head of the Met's 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 six males in custody and searches are continuing at five addresses. Detectives are carrying out extensive inquiries to determine the full facts behind the attack."
The investigation into the rush hour bombing - which injured 30 people - has seen three men aged 25, 30 and 48, detained in Newport, south Wales, a 21-year-old named Yahyah Farroukh arrested in Hounslow, west London, and an 18-year-old man detained at the Port of Dover.
A time limit on Mr Farroukh's detention is expected to expire today, while detectives have been given until Saturday to continue questioning the 18-year-old suspect.