An 18-year-old man was arrested on Saturday in the port area of Dover in connection with the Parsons Green bombing, Scotland Yard has confirmed.
Metropolitan Police Deputy Assistant Commissioner Neil Basu said that the arrest was “significant”, but added: “Although we are pleased with the progress made, this investigation continues and the threat level remains at critical.”
The man remains in custody at a local police station and will be transferred to a south London police station in due course, a police statement reads.
Home Secretary Amber Rudd described the arrest as “very significant”, but added: “The operation is ongoing.”
The suspect was arrested under section 41 of the Terrorism Act 2000 which gives police the power to arrest someone suspected of terrorism-related offences without a warrant.
These powers allow the extended detention of suspects without charge beyond the maximum four days available under the law that governs most other arrests.
The teenager’s capture took place in the port area of the city, which is the busiest ferry hub in Europe and serves as a commercial gateway to the French coast, including Calais and Dunkirk.
Basu urged the public to remain as “vigilant” as “our staff, officers and partners continue to work through this complex investigation”.
He added: “We are not, at this time, changing our protective security measures and the steps taken to free up extra armed officers remain in place.
“This arrest will lead to more activity from our officers. For strong investigative reasons we will not give any more details on the man we arrested at this stage.”
Detectives from the Met’s Counter Terrorism Command are continuing to urge anyone with information about the terrorist attack to contact police.
Thirty people are known to have been injured during the attack in which an improvised explosive device was detonated on a tube at Parsons Green Underground Station at around 08:20am on Friday.
So far, detectives have spoken to 45 witnesses and continue to receive information from the public to the confidential anti-terrorist hotline, police added.
A key strand of the police investigation has focused on CCTV as officers comb through footage to establish who planted the device, and when and where it was placed on the train.
Security minister Ben Wallace suggested CCTV images of the bomber could be released as part of the manhunt for those responsible, but Scotland Yard subsequently denied there were any plans to do so.
The public has sent 77 images and videos to investigators via the UK Police Image Appeal website.
Anyone with footage or images from the incident is urged to upload them at www.ukpoliceimageappeal.co.uk where they will be looked at by investigators.
The UK terror threat level was raised on Friday from severe to critical following the attack in which the bomb reportedly failed to fully explode.
Passengers fled in panic after the blast. Some suffered burns and others were injured in a stampede to escape but health officials said none were thought to be in a serious condition.