London Metropolitan Police detained a 30-year-old man in connection with the ongoing investigation of the latest terrorist attack in London, a statement released by the police said on Wednesday.
On the review into MI5 and the police, she said: "We will look at how the processes were followed, what they did".
Redouane, 30, went by the alias Rachid Elkhdar and claimed to be Moroccan or Libyan, police said.
Seven victims were killed and dozens injured in the spree, which ended when armed police shot dead the knife-wielding extremists just eight minutes after the first emergency call.
According to the Italian publication Corriere della Sera, Zaghba was stopped in 2016 when trying to catch a flight to Turkey, before travelling to Syria.
The third attacker was named as Youssef Zaghba, an Italian national of Moroccan descent, who was living in east London. The parents lived for a time in Morocco before separating when the mother returned to Italy and re-established herself in Bologna.
However they also said, "there was no intelligence to suggest that this attack was being planned and the investigation had been prioritised accordingly".
London's Metropolitan police, after Saturday's attack, informed Italian authorities of Zaghba's involvement in the attack and requested any background information about him. A new search was underway Tuesday in Ilford, just north of Barking.
Since the attack, he has said he fully supported the actions of the police. All three of the attackers were shot dead by police.
Thousands of bouquets and messages have been laid near London Bridge since the terror attack, the second to strike the capital in three months.
His comments came as a debate over police numbers, and the link between cuts in 2015 by then home secretary Theresa May and the rise in terror attacks, became the hot topic of the British general election campaign.
The other slain assailant was British citizen born in Pakistan, Khuram Butt, 27, who had been known to security services.
"I am not surprised that Khuram Butt carried out the terrorist attack and there are serious questions for the authorities", Shafiq said.
Butt is a father of two and had previously worked in KFC and in the customer service for the London Underground as a trainee.
Following the attack, London Mayor Sadiq Khan said the threat level in the country is still "severe".
Between 2009 and 2016, the number of police officers fell by nearly 20,000, or around 14 percent, according to the independent Institute for Fiscal Studies think tank.
The Conservative Party's lead over Labour has narrowed markedly from 20 points or more when May called the election in April to a range between one and 12 points now, although the Conservatives are still widely expected to win a majority.
The number of police officers in England and Wales fell by nearly 20,000 between 2010 and 2016 - years when May, as home secretary, was in charge of policing.
Police said Tuesday he is from east London and his family has been notified.
A book of condolences will open on Tuesday at Southwark Council's headquarters in Tooley Street.
It had been set at "critical" in the days after the Manchester concert bombing on May 22 that killed 22 people - reflecting a judgment that an attack might be imminent because accomplices with similar bombs might be on the loose.
She defended the performance of the intelligence agencies in foiling attacks at a time when the "tempo is increasing" in a way not seen before.