The Italy international is involved in an ongoing probe by Italian investigators, who are looking into suspicious betting activity.
Tonali and Aston Villa's Nicolo Zaniolo were both interviewed by police in relation to alleged betting breaches, while Juventus' Nicolo Fagioli has also been named by prosecutors and subsequently banned for seven months.
Tonali was present at the Italian Prosecutor's Office on Tuesday and it has been suggested that he could also face a worldwide football ban if he is found guilty.
Tonali's agent, Giuseppe Riso, has spoken at an event at the Italian embassy and has claimed that his client is an addict.
He said: "He is playing his most important game - against betting addiction. He’s in shock, he’s very sad. He has to face this situation. He is training at the moment (at Newcastle).
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"He told me he trained very well. He can play Saturday.”
Tonali remains eligible for Newcastle but it remains to be seen if that changes as the investigation continues.
He will not be in the squad for Italy's clash against England on Tuesday, having left the group amid his police interview.