An 18-year-old man has been arrested in relation to the London underground attack on Friday.
The teenager was arrested by Kent Police in Dover on Saturday morning UK time under section 41 of the terrorist act.
The bomb went off on a carriage at Parsons Green on Friday, injuring at least 30 people, and the attack was claimed by Islamic State.
“We have made a significant arrest in our investigation this morning. Although we are pleased with the progress made, this investigation continues and the threat level remains at critical," deputy assistant commissioner Neil Basu said in a statement.
“The public should remain vigilant as our staff, officers and partners continue to work through this complex investigation. 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.”