Assistant Commander Mark Rowley said: "Inquiries are ongoing to confirm the identity of their accomplice".
The attack unfolded quickly, and police said officers had shot and killed the three attackers within eight minutes. May said Monday that 11 remained in custody and one was released without charge.
Local news reported that the 30-year-old died in her fiancé's arms.
This was the third terror attack in the United Kingdom in three months, following the auto and knife attack on Westminster Bridge in March, in which five people were killed, and the Manchester bombing less on May 22 in which 22 people were killed.
Australian Candice Hedge is also among the wounded, her mother told CNN Sunday.
The Wheatsheaf pub in London's Borough Market.
In an appearance on NBC's "Today Show", Conway said people should pay attention to what the president is doing, saying people in England had tried to inform authorities about the terrorists before the attacks happened.
"I know what it's like to live in London and live off your tips and I don't think those people should lose out because of these barbarous people". "Evil, evil people", he told The Guardian newspaper.
Instead they "started kicking them, punching them and took out knives".
Before the shots were fired, he heard someone shout "knives, knives, knives".
French Foreign Minister Jean-Yves Le Drian is due to visit Britain on Monday to speak to the injured French nationals, after President Emmanuel Macron said France was "more than ever at Britain's side".
Commuters saw uniformed police officers at Tube stations around London, an unusual sight for a city where officers are less visible on the streets than in other major global cities.
Uber also donated to #OneLoveManchester, the benefit concert organized by Ariana Grande. "A detachment of Islamic State fighters executed yesterday's London attack", read a message on the ISIS-run Amaq news site late Sunday night. "But we got to move on".
"A very high priority for us is to try to understand whether they were working with anybody else", she said.
Britain's general election will be held on Thursday as scheduled, and supporters of the opposition Labour Party accused May of politicizing the attack.
"This is what we must do if we are to come together as a country and tackle this extremism in our midst - not just violent extremism, but the whole spectrum of extremism, starting with the bigotry and hatred that can so often turn to violence too", the prime minister said. "GOD BLESS!" His criticism of Khan followed later on.