Friends of a man extradited to Italy on Tuesday on people smuggling charges say police have the wrong man.
Prosecutors believe Mered Medhanie, known as The General, is at the heart of the operation to smuggle migrants from Africa to Europe.
An Eritrean man authorities say is Mr Mered was held in Sudan in May and flown to Rome on Tuesday.
But the man’s friends told the BBC there had been a case of mistaken identity and he was innocent.
He was named by friends as Mered Tesfamariam.
A woman in Norway identified herself as the sister of the man arrested, telling the BBC’s Newsnight programme her brother was “completely innocent”.
But Britain’s National Crime Agency (NCA), that was also involved in the operation, said it was “too soon to speculate” about the claims.
“The NCA is confident in its intelligence gathering process,” a statement said.Media captionJournalist Meron Estefanos says she is certain authorities have the wrong man
An Italian police official told the BBC that he was unaware of any investigation into the identity of the suspected smuggler.
The BBC understands that the Italian police still believe they have the right person.
The NCA said it had tracked the suspect down to an address in Khartoum, where he was then arrested.
Images of him arriving in Rome were distributed by Italian police on Wednesday.
Hermon Berhe, who lives in Ethiopia, said he grew up in Eritrea with the man now in jail in Italy.
“I don’t think he has any bone in his body which can involve such kind of things,” he said. “He is a loving, friendly and kind person,” he told the BBC.
Meron Estefanos, a Swedish-Eri