Radja Nainggolan, Roberto Gagliardini and Ionut Radu have all tested positive for coronavirus, Inter have announced.
The Nerazzurri issued a statement on Friday, eight days before they are due to face Serie A rivals Milan in the derby, revealing the trio were all shown to have contracted Covid-19.
Tests on the players were conducted at the club's Appiano Gentile training headquarters.
"FC Internazionale Milano announce that Roberto Gagliardini and Radja Nainggolan tested positive for Covid-19 following checks carried out at Appiano Gentile in recent days," Inter said.
"Ionut Radu also tested positive this morning [Friday], after tests carried out yesterday. Further checks are scheduled for tomorrow."
Midfielder Gagliardini started Inter's previous two Serie A fixtures, scoring one and assisting another in the 5-2 victory over Benevento on September 30.
Nainggolan returned to San Siro for this season after spending the previous campaign back on loan with Cagliari, though his only appearance of the campaign so far was a 15-minute cameo off the bench against Fiorentina.
Back-up goalkeeper Radu has never started a Serie A game for Inter and his only league appearance with the club came as a substitute back in 2016.
The news represents a concerning outlook for football in Italy, with Juventus's top-flight meeting with Napoli, that was due to be played on October 4, having had to be called off.
Despite Juve confirming they were available to play the fixture, Napoli opted not to travel to Turin following advice from local health authorities after two of their players, Piotr Zielinski and Eljif Elmas, tested positive for Covid-19.
It could be that Juve are awarded the three points due to Gennaro Gattuso's side's no-show, with a league statement reading: "The Council of the Lega Calcio did also approve a set of rules that can lead to the postponement of a game only with several cases of players testing positive for the virus.
"These conditions can’t be applied to the current Napoli case at the moment and there are no decisions of the local authorities that prevent the game from being played."