A third person, already in jail, is also under investigation, Ansa reported on Wednesday, citing sources.
In a separate operation, Italy's anti-terror police arrested five people accused of planning to fight in Syria alongside Isis jihadists.
The arrests, which were the result of a large anti-terrorism operation, were made during dawn raids on Wednesday in the Italian provinces of Milan, Bergamo, Grosseto and a town in Albania.
The Isis-related probe began in October after authorities became aware that an Italian female convert to Islam, Maria Giulia Sergio, 28, had joined the ranks of Isis after marrying an Albanian with the same intention.
The couple and the husband's mother travelled to Syria via Turkey several days after their September wedding, police said.
He was immediately dispatched to an Isis training camp while Sergio was given weapons training and sent messages to friends celebrating the deadly January attack on French satirical magazine Charlie Hebdo.
Sergio persuaded her parents and a sister, also Muslim converts, to join her in Syria. The family had sold their furniture and requested passports before their arrests on Wednesday for “organizing a journey for terrorist ends” – a recently introduced offence which was applied for the first time in his case.
Five members of the husband's Albanian family were arrested, including his father, Baki Coku, 40, who was detained in Albania and is now subject to extradition proceedings. The suspects also include a Canadian long-time resident of Italy.
In an unrelated case, nine people are currently on trial in Albania on charges of attempting to recruit candidates for jihad in Syria and helping finance their trips.
Last Friday, Italy raised its terror alert level following the deadly attacks in France, Tunisia and Kuwait.
At least 37 people were killed and 36 wounded when a gunman opened fire on holidaymakers on a beach in the Tunisian resort town of Sousse.
Meanwhile in France, a businessman was found decapitated with Arabic inscriptions on his body at a gas factory near Lyon, while further afield in Kuwait, a suicide bombing at a mosque claimed by Islamic State jihadists killed 25.