FIFA was forced to cancel its scheduled press conference on Friday moments before it was about to begin at its headquarters here as Blatter is being questioned by representatives of the Swiss attorney general.
Blatter was scheduled to address the media at the press conference.
"The Office of the Attorney General of Switzerland (OAG) has opened criminal proceedings against the President of Federation Internationale de Football Association (FIFA) on suspicion of criminal mismanagement as well as - alternatively - on suspicion of misappropriation," the Swiss attorney general issued a statement on Friday.
"Since 27 May 2015, FIFA has been cooperating with the Office of the Attorney General and has complied with all requests for documents, data and other information. We will continue this level of cooperation throughout the investigation."
"Today, at the Home of FIFA, representatives from the Office of the Swiss Attorney General conducted interviews and gathered documents pursuant to its investigation. Fifa facilitated these interviews as part of our ongoing cooperation," the statement added.
"We will have no further comment on the matter as it is an active investigation."