The third London Bridge terrorist has been named as Youssef Zaghba, an Italian national of Moroccan descent.
Scotland Yard confirmed the identity of the 22-year-old, from east London, and said he was not a police or MI5 "subject of interest", despite Italian media reports suggesting he was.
The news came as detectives arrested another suspect at an address in Barking, east London. The 27-year-old was held under the Terrorism Act shortly after 8am on Tuesday.
According to the Corriere della Sera newspaper Zaghba's Italian mother lives in Bologna in the north of the country.
The paper said Zaghba was born in Fez in Morocco and had seasonal work in a London restaurant. It reported that he was stopped by Italian police in March 2016 at Bologna's airport trying to fly to Turkey and then on to Syria.
Italian intelligence officials reportedly communicated this to their UK counterparts.
The name was confirmed as MI5 and police faced questions after it emerged another of the three perpetrators, Khuram Shazad Butt, 27, had been investigated two years before the atrocity.