Seven men and five women have been released without charge
Counter-terror police arrested 12 people at addresses in Barking on Sunday in a bid to track down anyone linked to the three terrorists responsible for Saturday’s attack.
In a statement, Metropolitan Police said: “Family liaison officers have now deployed into all those families where we believe people to be dead.
“Family liaison officers have also been deployed to support one family where we believe one person is still missing.”
Khuram Shazad Butt, a 27-year-old British citizen born in Pakistan, and Rachid Redouane, who claimed to be Moroccan-Libyan, were named as attackers on Monday evening.
Assistant Commissioner Mark Rowley said Butt was known to the security services, but there was no evidence of "attack planning" by him.
On Sunday night it emerged that a Canadian woman killed in the London Bridge attack died in her fiance's arms.
London Bridge terror: Scenes as armed police respond Sun, June 4, 2017
At least two people have died after being after reportedly being struck by a van on London Bridge on Saturday night.
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Armed police responding to the incident at London Bridge
Christine Archibald is the first named victim of the London attack which killed seven people and critically injured 21 others.
Cassie Ferguson Rowe said her brother, Tyler Ferguson, held Ms Archibald and she died in his arms.
Writing on Facebook, she said: "Last night in London my baby brother lost the love of his life on the London Bridge.
"In a split second his entire life was ripped away from him. Hearing his painful sobs on the phone while he's alone trying to deal with this tears me apart.
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"I have no words. If you know Tyler, please be there for him now, and later when what happened sinks in, he's going to need us all."
Thousands came out to honour the victims of Saturday night's attack on Monday evening
Officers raided addresses in Dagenham and Newham in east London at around 4.15am on Monday morning, with a “number” of arrests made.
Witnesses reported hearing “gunfire and explosions” around the area, with helicopters also seen.
A Scotland Yard spokesman said: "At around 4:15am on Monday, 5 June, officers from the Met’s Counter Terrorism Command investigating the London Bridge terror attack entered two further addresses – one in Newham and another in Barking.
London Mayor Sadiq Khan (C), Home Secretary Amber Rudd (L) & her Labour counterpart Diane Abbott
"A number of people have been detained and are at present being spoken to.
"Searches are ongoing at both addresses."
The raids come hours after police stormed a flat in Barking, east London as part of the terror investigation.
Officers arrested 12 people on Sunday in connection with the incident which killed seven and injured dozens.