One neighbour, Ken Chigbo, said Butt has asked him about hiring a van hours before the attack took place.
Youssef Zaghba, 22, was the son of an Italian mother and a Moroccan father who had separated, and was registered as an Italian living overseas, said Daniele Ruscigno, mayor of Valsamoggia, near Bologna.
Police say he was not a "subject of interest" to police or the intelligence services.
Meanwhile, a man has been arrested on suspicion of terror offences by detectives investigating the London Bridge attack following an early morning raid at an address in east London.
Security agencies on Tuesday searched the hotel in Mujahidabad area in Karachi owned by an uncle of Khuram Shazad Butt, 27, who was among the three terrorists shot dead by police after their Saturday night terror.
Italian authorities put him on a watch list and flagged his presence to Moroccan and British counterparts, according to the Corriere della Sera newspaper.
Before the recent attacks, Brexit and domestic issues such as the state of the health service and the cost of care for the elderly had dominated the election campaign. The company was looking into Italian media reports that Zaghba also was a former employee. No arrests had been made, police said.
Transport for London (TfL) confirmed that Butt worked for London Underground for just under six months as a trainee customer services assistant, leaving in October a year ago.
It is thought that Choudary played a key role in Butt's radicalization, according to a British government official who spoke on condition of anonymity because he was not authorized to talk about the ongoing investigation.
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Former President Obama delayed the project in December by refusing to grant the Army Corps of Engineers an easement for the lake. The pipeline's developer, Energy Transfer Partners , successfully completed building the $3.8 billion pipeline in mid-May.
Neighbors described Butt as an avid weightlifter and Transport for London confirmed he worked for London Underground in customer service before leaving last October. At least seven people were killed and dozens were injured.
He was stopped at Bologna airport on 15 March a year ago travelling with just a backpack, very little money and a one way ticket to Istanbul; crossing the border from Turkey into Syria had become a regular route for those seeking to join rebels fighting the Bashar al-Assad's regime.
When stopped the previous month at Bologna airport en route to Turkey, from where he meant to cross the border into Syria, the 22 year old reportedly declared "I am going to be a terrorist".
Collina said Zaghba was monitored by Italian intelligence agents each time he came to Italy to visit her after his initial run-in with airport authorities.
"We did everything we could but there was not sufficient basis to prove he was a terrorist, he was a suspect based on types of behaviour".
"It is seeking to project its influence and maintain its relevance by inspiring, encouraging, and - though there does not appear to be evidence of this in the latest United Kingdom plots to date - directing attacks in Europe and elsewhere", he said.
The main evidence comes from his appearance in a Channel 4 documentary, The Jihadis Next Door, broadcast previous year.
As the row threatened to overshadow the final days of the general election, Theresa May was facing questions over the actions of the intelligence agencies and the Home Office at a time when she was home secretary. A string of opinion polls over the past couple of weeks have pointed to a narrowing in the gap between her Conservative Party and the main opposition Labour Party.
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.
Associated Press writers Paisley Dodds and Raphael Satter reported this story in London and AP writer Kathy Gannon reported from Pakistan.