London police have arrested another man suspected of a connection to the lethal attack on London Bridge.
Zaghba was "not a police or MI5 subject of interest", it added, an assertion that seemed to conflict with accounts in the Italian media.
A total of 48 people were injured and London hospitals are continuing to treat 29 people - 10 of whom are said to be in a critical condition.
Thomas, 45, was walking with his girlfriend over the bridge when the attack began on Saturday night.
Dozens of people gathered in driving rain at the end of London Bridge, where a growing mound of flowers sits beside a police cordon.
Eight people were killed in London on Saturday night when three terrorists ran into pedestrians on London Bridge before stabbing people in the area.
All three suspects were confronted and shot dead by armed officers within eight minutes of being called, police noted.
"We are so proud of Kirsty's courageous actions which demonstrate how selfless, caring and heroic she was, not only on that night, but throughout all of her life", they added.
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Butt had featured in a Channel 4 documentary The Jihadis Next Door, broadcast previous year.
Less than two weeks earlier, a suicide bomber had killed 22 adults and children at a pop concert in Manchester and, in March, five people died after a vehicle was driven into pedestrians on London's Westminster Bridge.
A panel of speakers at the East London Mosque said they would work to combat extremists' "twisted narrative and their perversion" of religion. Police have not released the identity of the third attacker.
Police had already named Butt and Redouane, a 30-year-old who claimed to be Moroccan and Libyan.
The first victim has been named as Chrissy Archibald, a Canadian bride-to-be who volunteered at a homeless shelter.
Ms Delcros is said to have been seriously injured.
Neighbours in his east London neighbourhood of Barking said he spoke with a heavy London accent.