He was arrested at a business premises in Wexford Town yesterday afternoon, amid suspected links to terrorist Rachid Redouane who had lived in Dublin.
Irish media reported that an Irish identification card was found on Redouane's body, and Prime Minister Enda Kenny confirmed that one of the attackers lived in Ireland for a time but did not attract the attention of law-enforcement.
According to sources, gardai believe the man has been living and working in Limerick for some time and that he may have lived elsewhere in Ireland prior to that. The man detained in Limerick, who used Redouane's PPS number and had other documents in his name, was released without charge.
While his marriage, which has since broken up, dated to 2012, gardaí have established Redouane spent a prolonged period in Dublin in 2015.
Corriere wrote that Zaghba was stopped at Bologna airport in 2016 when he was trying to fly to Syria and that Italian authorities had tipped off Britain about his movements.
The UK police and security services are under mounting pressure over Saturday's attack, which killed seven people, after it emerged that two of the three attackers had known histories of extremism.
The suspect is being questioned about documentation connected to Rachid Redouane, one of the three killers behind the weekend attack.
At the time of the attack he was working in a London restaurant and continued to have contacts with his mother in Italy, which he visited previous year, Corriere wrote.
Butt had featured in a Channel 4 documentary past year, The Jihadis Next Door, where he was seen praying in a group in Regent's Park with what appeared to be a black extremist flag.
The nature of the card has not been divulged but sources said it was most likely to have been either a GNIB identity card or an Irish EU Fam Card, a type of residency card for non-EU citizens linked to an EU resident in Ireland.