Italian Prime Minister Matteo Renzi's government has been put under pressure after one of its junior members was put under investigation on Friday. Undersecretary for agriculture Giuseppe Castiglione is suspected of bid-rigging to obtain a contract for a large migrant centre in Sicily, AFP writes.

Renzi has so far defended Castiglione, assuring AFP that he would not ask him to resign unless he is convicted. Yet as Castiglione is but one of many prominent figures that have come under scrutiny for illegal activity in recent days, this assurance is likely to be put to the test.

This investigation comes in the wake of an intensification of Italy's crackdown on mafia-like activities. It began last Thursday,  when Italian military police arrested 44 people in several raids centered in the province of Rome. Suspects include a former president of the regional council of Rome as well as several other key regional politicians and businessmen.

These arrests have since been followed up by investigations into an additional 21 people, among which are Castiglione as well as several other politicians and entrepreneurs, according to la Repubblica, a major Italian newspaper.

All of these people are being variously suspected of mafia-association, corruption, bid rigging and fiscal fraud.

These arrests are, in turn, part of a major operation against a Roman mafia organisation nicknamed ‘Mafia Capitale’. A crackdown on the organisation was initiated in December 2014 by the military police, in which 37 people were arrested, including the organisation's leader Massimo Carminati, la Repubblica reports.

Carminati, dubbed ‘the King of Rome’, was a member of a neo-fascist terrorist organisation in the 1970's, after which he rose to prominence in Italian organised crime.

This new wave of arrests is causing deep unease, as they reveal that Castiglione and several others are suspected of paying bribes in order to gain lucrative contracts for the management of migrant centers. Intercepted phone calls, Italy's main source of evidence in mafia and corruption cases, paints a chilling picture: "If you give me 100 people we make one euro for each... something like that, you know?” one official was caught telling a candidate company according to la Repubblica.

Italy has been struggling with an influx of migrants arriving by sea over the Mediterranean for several years, the intensification of which has prompted EU intervention, with a plan for humanitarian and military action being currently debated in Brussels.

The fraudulent management of these humanitarian efforts is causing increasing dismay, with the UN's refugee agency calling the hints at mafia involvement in the management of migrant centers "despicable", according to AFP.

The case of the migrant centers is but the most gruesome of the activities under scrutiny, however. These all follow a common pattern of payments in various forms offered in exchange of favours by officials. Thus, a former president of Rome's municipal council was charged with favouring a cooperative headed by the noted criminal Salvatore Buzzi, now in jail. "I just bought Coratti, he's with me now," Buzzi said of the official in an intercepted phone call, la Repubblica writes.

The scandal is also pointing to mafia involvement in the campaign of Gianni Alemanno, former mayor of Rome and Minister of Agriculture, during his election campaign for the European parliament in 2014. A clan of the Ndrangheta, a major criminal organisation based in Calabria in southern Italy, is thought to have been contacted to support his campaign, la Repubblica reports.

With so many scandals surrounding Roman politicians, reactions in Italy have been polemical. "We need to stop the boat departures and stop the public tenders immediately," Matteo Salvini, head of the anti-immigrant Lega Nord party, said following the arrests, according to Reuters.

Salvini, joined by the protest party 5-Star Movement, further called for the resignation of the mayor of Rome, Ignazio Marino, who himself has declined any involvement and aims to complete his term.

Marino's government hails from Renzi's own Democratic Party. The PM has thus defended the mayor, telling AFP that "Marino is not part of this criminal clique," referring to the fact that much of the corruption in Roman politics was already well established when the latter began his term in 2013.

Aside from Mafia Capitale, Italian prosecutors are investigating further allegations of corruption surrounding the award of public contracts for the Milan Expo and the Venice flood barrier corporation, Reuters reports.