Police in Sicily on Wednesday arrested two Italians and two Tunisians accused of trafficking migrants from North Africa to Europe via Italy.
Police named the Italian suspects as Felice Montalbano and Pietro Bono.
Montalbano and Bono were held at their homes in the town of Menfi in the province of Agrigento.
Police did not state where the Tunisian suspects were held.
The suspects face charges of "belonging to a human trafficking gang that abetted illegal immigration and which smuggled tobacco to Italy".
The alleged gang operated a lucrative migrant trafficking route from Tunisia's coat to the western Sicilian port of Trapani, according to investigators.
Montalbano and Bono are accused of sheltering members of the gang and providing it with logistical support.
Wednesday's arrests follow a probe by prosecutors in Palermo which led to the arrest earlier in June of the alleged gang's head Jabraane Ben Cheikh and his right-hand man, Tarek Ben Massoud - who are both Tunisian nationals.
Ben Cheikh and Ben Massoud are currently detained at the high-security Sollicciano Prison near Florence in Italy's central Tuscany region.
Police in Sicily on Monday arrested a Nigerian, a Bangladeshi and Gambian accused of people trafficking after a boat with 267 migrants on board arrived at the port of Pozzallo. Police also held three Ukraians after 100 migrants landed in eastern Sicily.
Around 84,000 migrants arrived in Europe this year through 21 June, nearly 85 percent of them in Italy, according to the International Organisation for Migration (the United Nations migration agency).
