Signori was one of 16 people, accused of being involved in the rigging of matches to fix bets, arrested. The police are investigating a total of 18 matches.
Some of the other individuals held are said to include former Serie A players, current Serie B and C players, and club directors, according to BBC News.
Several matches from the recently-completed football season in Italy are under the spotlight, including a Serie A meeting between Inter Milan and Lecce, as well as games involving Atalanta and Siena. The two latter clubs gained promotion to the Italian top flight for next season.
Signori, who was top scorer in Serie A on three occasions with Lazio, was arrested after police in towns and cities across Italy issued detention orders.
The 43-year-old played 28 times for his country.