"Detectives investigating the London Bridge terror attack have carried out a search warrant at an address in east London in the early hours of Wednesday", police said in as statement.
Police on Tuesday also arrested a 27-year-old man in Barking on suspicion of violating the Terrorism Act and a residence there was being searched.
Eight people were killed in London on Saturday night when three terrorists ran into pedestrians on London Bridge before stabbing people in the area.
Armed officers killed all three attackers within eight minutes of receiving an emergency call. Police shot and killed all three.
Closed circuit TV footage, which appeared online and in British media, showed the attackers - Khuram Butt, Rachid Redouane and Youssef Zaghba - cornering a victim and starting to stab him before police are seen arriving and opening fire.
Police said the body had not been formally.
And his extremist views had reportedly prompted numerous people to go to the authorities.
Police have arrested six men in actions directed against terror in the U.K.as a tense nation begins voting in a national election. They returned the device but pointed him out to London as a possible suspect, Amato said.
There were more than 100 people injured in the Manchester and London attacks combined.
After that, Amato said, any time Zaghba was in Italy, he was always tracked by Italian intelligence officers. She sensed what she calls "melancholy" in his voice and, in retrospect, said he was making his farewell call. Asked what she would say to the victims' families, Collina said, "I feel ashamed when I try to think of words".
Butt had worked for the London Underground for six months a year ago as a trainee customer services assistant, Transport for London told the BBC.
He added: "We are paying a heavy cost in these attacks".
Youssef Zaghba is said to have been stopped by Italian officers trying to travel to Syria a year ago.
Zaghba visited her at her home near Bologna several times and in March 2016, after being stopped at Bologna airport, he was investigated for possible worldwide terrorist activity but released, according to the newspaper.
This year, she said, he was an intern at Eman Channel in London, working as a sound technician at the TV station.
On Tuesday, the third attacker was named as Youssef Zaghba, 22, an Italian national of Moroccan descent who was living in east London.
"We saw him many, many times around here", said Salahudeen, a 40-year-old driving instructor.
- The names of the 12 people arrested after raids in Barking have not been released.
The Islamic State group has claimed responsibility for the brazen attack that started on London Bridge, then continued in the streets surrounding Borough Market.