Metropolitan police searched a house in east London on Sunday in an investigation into a "terrorist incident" involving a knife attack at Leytonstone tube station.
Scotland Yard thanked members of the public for information they have provided about the attack, which took place early on Saturday evening.
"As a result of information received at the time from people who were at the scene and subsequent investigations carried out by the Counter Terrorism Command (SO15), I am treating this as a terrorist incident," Commander Richard Walton, leader of the Met's counter-terrorism command, said.
Following the incident, bloody images and eyewitness accounts emerged on social media.
In one video, a passerby can be heard shouting "you ain't no Muslim bruv" after the attacker claimed his actions were in response to Britain's airstrikes on ISIS jihadis in Syria.
Londoners have since adopted the hashtag #YouAintNoMuslimBruv to show solidarity with the vast majority of Muslims who have no involvement with violence.
Police said mobile phone footage captured at the time of the attack could be integral to their investigation, and urged those who had filmed the incident to work with them.
"I am aware that there were a number of members of the public in the underground station who filmed the suspect on their mobile phones during and after the attack," Walton said, "and I would urge them to come forward and speak to us and share with us the filming that they carried out."
Two men were injured and one woman was threatened in the attack, police confirmed.
One man was being treated in an east London hospital for "serious knife injuries" after police gave him first aid at the scene. He remains in a stable condition.
The other man did not require medical attention for his minor injuries and left the scene, while the woman, police said, remained unscathed.
After arriving on the scene, officers from Waltham Forest borough were threatened with violence when confronted by a man still wielding a knife.
The man was restrained and arrested for attempted murder, before being taken to an east London police station where he remains.
Waltham Forest Detective Superintendent Jacqueline Sebire thanked police for their quick response, noting that the incident highlighted the kind of risks faced by officers daily.
"I would like to take this opportunity to praise not only their bravery in confronting the man who was in possession of a knife," Sebire said in a statement, "but also their quick response in providing first aid to the victim whilst offering reassurance to the many members of the public who were travelling through the underground.
"We will continue to provide a visible presence in the area if anyone wishes to ask for advice about personal safety. We also remain in contact with community groups and local partners."
"What happened last night at Leytonstone station is totally unacceptable, and we strongly condemn this," imam Imran Patel from Leytonstone Islamic Association told Sky News on Sunday.
Imams from Leytonstone Islamic Association condemn tube stabbing that took place in the area on Saturday https://t.co/SIKKfPR5l9
Patel said the Leytonstone Islamic Association did not know the attacker, who was not part of their congregation. "For his motives and his actions, only he can answer himself," Patel said.
He went on to condemn all violent acts and terrorism, adding that Leytonstone is a well-integrated and multicultural community.
"We live in peace and harmony," Patel said.
Train services were initially suspended following the attack, but resumed in the early hours of Sunday.