Siena, as well as fellow promoted team Atalanta, have been named by police as two of several clubs whose matches in the Italian second tier last season are being probed over illegal betting and potential score manipulation.
The Italian Football Federation has launched an inquiry with the two sides, who deny any wrongdoing in an affair which has led to former Italy striker Giuseppe Signori being arrested, waiting to see if their promotions may be affected.
Siena have continued planning for next term back in the top flight and Monday's statement said Sannino, who coached modest Varese to the Serie B play-offs last season, had penned a two-year contract.
The Tuscan outfit were without a coach after Antonio Conte left following their promotion to take the reins at his former club Juventus.
Once mighty Juve have struggled since being demoted in a match-fixing scandal five years ago and one state prosecutor said on Monday that the new probe into possible irregularities in Serie B could turn out to be just as serious as the 2006 case.
Investigators have said a handful of Serie A games may have been affected this time and the Italian newspapers have been awash with stories about the fresh scandal.
In the 2006 affair, which revolved around corrupt referees rather than betting, Juve general manager Luciano Moggi was banned for five years from football for his involvement.
In a separate development to the new case and the criminal trial still going on into the 2006 scandal, the Italian Football Federation met on Monday to discuss banning Moggi for life with a final decision due soon.
