SAO PAULO—A former Italian mafia boss convicted of murdering more than 20 people was arrested in Brazil on Tuesday shortly after dropping off his two young children at school, more than 30 years after his escape through the window of an hospital room in Italy.

Pasquale Scotti, 56 years old, was a leader of the New Camorra criminal organization and "a very dangerous fugitive," an Italian police official said. He escaped from a hospital near Naples in 1984 and then vanished. Found guilty in absentia in Italy in 2005, Mr. Scotti was sentenced to life imprisonment for murder, including organizing the killing of a rival's girlfriend, along with extortion and other crimes.

"Sooner or later justice will apprehend you. The state doesn't forget," said Fausto Lamparelli, head of the Naples section of the Italian police's serious crimes unit. Italian Interior Minister Angelino Alfano wrote on his official Twitter account that Mr. Scotti's arrest was a "win for Team Italy."

Mr. Scotti was detained in the northeastern Brazilian city of Recife at about 7:00 a.m. local time. He arrived in Brazil in 1986 using false identification documents, Brazilian and Italian police said Tuesday at a news conference in Brasília. He married a local woman, with whom he has two children, and set up businesses in the area, including a real-estate brokerage and a fireworks factory, police said.

Mr. Scotti offered no resistance and told police that he wanted to forget his past in Italy. His wife of 18 years and the rest of his Brazilian family didn't know about his criminal past, a Brazilian official said. Efforts to reach Mr. Scotti's lawyer were not successful.

Italian police tracked Mr. Scotti down while investigating suspicious activity by Italian nationals in connection with Brazilian counterparts. Police officers began to think the man known in Brazil as Francisco de Castro Visconti was in fact Mr. Scotti, and a check of his fingerprints confirmed their suspicion.

The investigation is still ongoing, so many details are still classified, Brazilian police said. Mr. Scotti is being held in a jail in Recife, and Brazil's Federal Police have requested a transfer to a maximum security prison. The country's Justice Ministry has 90 days to decide on his extradition.

Mr. Scotti was arrested in Italy in 1983 after a shoot-out with police. Italian police officers said he cooperated with authorities there for a year before escaping through a window in his hospital room on a low floor in late 1984. Police suspect he was assisted by Camorra associates, but appeared to cut off ties with them after he left Italy.

"He left no traces. He just vanished," investigators were reported saying at the time.

Authorities say Mr. Scotti was a close ally of Raffaele Cutolo, head of the New Camorra group that participated in, and eventually lost, a bloody mafia war with members of the New Family crime group that led to almost 1,000 homicides from 1979 to 1984.

The New Camorra dominated Naples and most of the Campania region in the 1980s, according to Italy's anti-mafia investigators. The organization reached its height in the early part of that decade, when it had about 7,000 members. Its activities included cigarette smuggling, extortion and drug trafficking, and it made a fortune speculating on reconstruction after the big earthquake that struck Campania in 1980, authorities said.

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