Police found what they described as extremist material on his cellphone. His mother is Italian and still lives there.
The attack left seven people dead and dozens wounded before police shot dead the three attackers, who wore fake suicide vests.
Zaghba, an Italian national of Moroccan descent, was the youngest of the attackers and was allowed to enter the United Kingdom and had been living in east London before Saturday's attack. The second man, Rachid Redouane, had not aroused any suspicions. Butt was featured in a 2015 documentary titled "the Jihadi's next door" and was known to United Kingdom authorities.
Both British authorities and Ireland's Police Commissioner Noirin O'Sullivan have said they had no evidence Redouane was involved in any terror cell during his time in both countries.
Police said Tuesday that his family has been notified.
Xavier Thomas (45) had not been seen since Saturday night.
"I am going to be a terrorist", he told officials after he was stopped.
Reaction to the attack has dominated the final days of campaigning before Thursday's general election, with opposition Labour Party leader Jeremy Corbyn and others criticizing May for cutting police numbers by roughly 20,000 during her tenure as home secretary.
The inquiry was "prioritised in the lower echelons of our investigative work", Mr Rowley added.
"We received confirmation of the new toll this morning. We will probably discover communications during that period that we couldn't access that would have change the situation", the spokesperson said.
London police said all 12 people held since the attack late Saturday from the Barking neighborhood in the east of the city had been freed without charge.
The family home of killer number one, Khuram Butt, age 27, was raided in Pakistan.
The operation took place overnight and searches are ongoing at the properties, the force said.
They saw a man dragged from a house and arrested while armed officers led three women out to a neighbouring garden and told them to keep their heads down.
A French national was also killed in the attack, according to foreign minister Jean-Yves Le Drian, which the BBC understands to be Mr Pigeard.
Butt, 27, was previously known to authorities, but there wasn't enough intelligence to suggest he was planning an assault. Despite his appearance in the documentary, Butt was a trainee within the London metro system and was only asked to leave after his poor attendance record.
It is also reported that Butt was reported to the police as a potential danger two years ago.
The Islamic State terror group has claimed responsibility for the atrocity, which sparked fears that Britain is in the grip of a wave of copycat incidents. Since the attack, he has said he fully supported the actions of the police.
"It is clear that Anjem Choudhury and his band of terrorist sympathizers were known to the police for many years".
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