An 18-year-old man has been arrested in Dover on the morning of 16 September in connection with the Parsons Green terror attack.
London's Metropolitan Police have issued the following statement:
Parsons Green attack
At around 8.20am on 15 September, an improvised bomb partially detonated on a London rush-hour Tube carriage which had stopped at Parsons Green station on the District line. The blast, which injured 29 people, occurred in the south-west of the city, on a train full of commuters including children on their way to school.
Prime Minister Theresa May, acting on the recommendation of the Joint Terrorism Analysis Center, raised the country's threat level from "severe" to "critical", the highest possible level. May said military troops would augment the police presence in a "proportionate and sensible step."
A manhunt began for the perpetrator of the fourth terror attack in the capital this year.
Experts said the bomb, which was hidden in a plastic bucket inside a supermarket bag, only partially exploded. The blast caused no serious injuries.
The Islamic State has claimed responsibility for the attack, although this has not been corroborated.