The investigation was opened by Michael Garcia, the former U.S. attorney who was appointed last month to head the investigatory chamber of the ethics committee responsible for dealing with corruption in soccer's governing body.
Bin Hammam, a former head of the former Asian Football Confederation, had already been provisionally suspended.
"These proceedings follow the provisional banning for Bin Hammam for 90 days as established by the ethics committee on July 26 after a preliminary investigation of the case," FIFA said in a statement.
FIFA is collecting further evidence over allegations that Bin Hammam tried to bribe Caribbean officials in the run-up to last year's FIFA election.
It will also investigate allegations of financial wrongdoing while he was head of AFC.
Bin Hammam, a former member of FIFA's executive committee, challenged Sepp Blatter for the presidency of football's world ruling body last year.
Bin Hammam withdrew his candidacy days before the June election over allegations that he had tried to buy the votes of Caribbean officials by handing them $40,000 each in brown envelopes at a meeting in Port of Spain.
Blatter was subsequently re-elected unopposed for a fourth term as FIFA president and Bin Hammam was banned for life.
CAS upheld Bin Hammam's appeal against a life ban, saying FIFA's evidence had been insufficient. However, it said the decision was not "an affirmative finding of innocence" for Bin Hammam, and that the case could be re-opened with new evidence.