Italy's mafia is renowned all over the world for its brutality and omnipresence in the south of the country. Judicial documents have now revealed surprising details about the organization's revenue sources in Rome. According to the Italian news agency ANSA, a mafia network run by Massimo Carminati — known in Italy as the "last king of Rome" — makes most of its revenue by extorting money destined for the country's Roma population and immigrants.

The documents explain how the mafia bribes officials to gain access to profitable public work contracts. According to Italian investigators, the mafia's network reached as far as into the mayor's office, where high-ranking officials were allegedly bribed with payouts of as much as $18,000 a pop. In return, mafia members won valuable contracts to manage the accommodation of refugees, the city's waste collection and even parks.

In an intercepted phone call, suspect Salvatore Buzzi was quoted saying that "drug trafficking earns less." Other evidence suggests that Rome's mafia has largely given up on trafficking in drugs and has instead embraced the more profitable "immigration business," according to investigators.

"We closed this year with turnover of  [$50 million], but ... our profits all came from the gypsies, the housing emergency and the immigrants," Buzzi reportedly said in a phone call.

On Dec. 3, 37 people were arrested for alleged mafia activities in Rome and charged with extortion, corruption, fraud, money laundering and embezzlement. When investigators searched suspects' apartments and offices, they seized items worth $247 million, according ANSA. Among those targeted was Gianni Alemanno, who was Rome's mayor from 2008 until last year, as well as Italo Walter, currently the city's anti-corruption chief. Alemanno was not arrested but was notified that an investigation against him had been launched.

The alleged corruption network could be much bigger than previously assumed. As of Tuesday, about 100 officials, business people or politicians were under investigation.

Traditionally, the mafia has made money by trafficking in drugs or demanding 'protection money' from restaurant or hotel owners. But last month, AFP reported that the mafia in Sicily may be increasingly benefiting from the arrival of refugees. As hotels were turned into immigrant centers, state subsidies "caught the Mafia's eye." Aid organization Caritas warned that criminal groups could exploit the system.

Mario Michele Giarrusso, a Sicilian senator from the Five Star Movement political party, was quoted as saying: "The interest is to open as many as possible and keep the migrants there. The longer they keep them, the more money they bring in. ... It's a business all right. These migrants die in the Strait of Sicily just to bring millions of euros to the mafia."

According to the news agency, hotels that accommodate immigrants receive about $37.50 per immigrant each day. Given that there are currently more than 30,000 migrants in Italy, that means the business is more than $1.24 million a day, according to AFP. At least 32 hotels, schools or holiday resorts have been transformed in western Sicily's Trapani region alone.

Elsewhere, the presence of migrants has caused anger. In Rome, police had to intervene in November when local residents attacked a center for young immigrants. Despite opposition, more centers are planned in Rome and surrounding areas in the near future.

The ongoing investigation is supposed to prevent Rome's mafia network from further abusing the country's immigration system as a revenue source.

Meanwhile, consumer rights groups have expressed outrage over the corruption scandal.

"The investigation into the 'Mafia capital' reveals a disgusting, horrifying situation which goes beyond even the darkest hypothesis," consumer rights groups Adusbef and Federconsumatori said  in a statement. They went on to describe the allegations as "a democracy emergency."