Butt, who The Guardian said was also known as Abu Zaitun, was known neighbours by the nickname "Abs/z". He said the vehicle was seen going the wrong way down a one-way street and was later seen speeding off, followed closely by a small red auto.
Butt, 27, was a British citizen who was born in Pakistan.
The attackers, wearing fake suicide vests, were shot dead by eight officers after police opened fire with a hail of 50 bullets. The three assailants were shot dead by police. Other attacks have been committed without direct ISIS involvement by terrorists who are sympathizers of the radical group.
Eleven people are being held after police raids in Barking on Sunday.
Jeremy Corbyn, leader of the main opposition party, has slammed May for the cut in police numbers, saying that "you can not protect the public on the cheap", and promising to recruit another 10,000 police officers if he is elected into power.
"I am pleased that the Prime Minister is speaking about conversation: it implies that we must listen to one another and work together to be part of a truly United Kingdom".
The UK goes to the polls on Thursday in an early general election called by May.
"As we mourn Ms. Archibald, along with the others taken from their families too soon and in such a senseless way, we give thanks to the police and first responders who were there to serve and protect".More news: Ariana Grande concert raised $3.5M for Manchester charity
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One person is still believed to be missing, the force said. "He has more important things to do than respond to Donald Trump's ill-informed tweet that deliberately takes out of context his remarks urging Londoners not to be alarmed when they saw more police - including armed officers - on the streets". Metropolitan Police Commissioner Cressida Dick said she wouldn't release further details in what she described as a fast-moving investigation.
It comes as police have searched more addresses in east London. "America grieves with you", Lukens said.
Rowley said the security services had stopped 18 plots since 2013, including five since the Westminster attack two months ago.
The bombing killed 22 people who were at the arena for an Ariana Grande concert.
It was lowered once intelligence agencies were comfortable that this wasn't the case.
While reports in the Irish press stated that one of the three attackers has a Scottish wife.
But as is the case in many of these incidents, authorities were well aware of exactly who at least one of the bridge attackers was.
A woman reacts near the scene of the recent attack during a minute's silence (Picture: Reuters) People observing a minute's silence in St Ann's Square, Manchester, in honour of the London Bridge terror attack victims.
It provided a kaleidoscope of London's diversity, with Buddist monks in saffron robes, Christian clerics in purple cassocks and Muslims in black T-shirts bearing the words "I am a Muslim: Ask me anything".