Baseball reviewed a draft Tuesday at the Manhattan office of DLA Piper, the law firm that Mitchell chairs, a baseball official said, speaking on condition of anonymity because Mitchell hasn't authorized any statements.
The report likely will be released Thursday, and commissioner Bud Selig does not plan to attend Mitchell's news conference, the official said. Selig could have his own news conference or hold a conference call, he added.
Baseball officials have said for several weeks that management would be able to examine the report on performance-enhancing drugs a few days before it is made public to make sure it does not contain any confidential information that if released would violate the collective bargaining agreement between players and owners.
The joint drug agreement, which has been part of the labor contract since September 2002, prohibits the commissioner's office, teams and consultants from disclosing player test results, treatment and other information except in very limited, specified circumstances.
The start of baseball's review first was reported by the Daily News on its Web site.
Mitchell, a former Senate Majority Leader, is a director of the Boston Red Sox and served on one of Selig's economic study committees. Selig hired him in March 2006 to investigate drug use in the sport.
He's expected by many in baseball to be critical of the sport for being slow to react to its drug problem in 1990s and beyond. What they will be looking to see in his report is how he parcels blame among commissioner Bud Selig, club owners, general managers, other team employees, the players' association and players themselves.
The revelation of players who have not yet been publicly linked to drug use figures to be the most sensational part of the report. Media reports have linked an array of All-Stars and MVPs to performance-enhancers in recent years, among them Barry Bonds, Jose Canseco, Ken Caminiti, Juan Gonzalez and Mark McGwire.
Bonds, indicted last month for perjury and obstruction of justice over his 2003 testimony in the BALCO drug case, has denied knowingly using performance-enhancers, as have Gonzalez and McGwire.
AP Sports Columnist Jim Litke contributed to this report.