Baseball has been conducting its own investigation into these allegations. Selig said he could not comment on the specifics of the case while it was ongoing, but he did expand on the reason for baseball's investigation.
"I'm going to talk about Biogenesis," the Commissioner said. "There is not a lot, obviously, that I can say. I'm sometimes mystified [by] people sometimes critical of baseball who will say a lot of different things: 'Oh, this is about some kind of retribution,' or, 'This is something to do with [Selig's] legacy,' or whatever the case may be.
"Look, the history of our sport is thus: We went through the cocaine era of the '80s. No drug-testing program, which was quite sad. We went through the Pittsburgh drug trials, which many of you will remember. Very sad. Twenty-nine people were convicted, four went to jail, if memory serves me correctly. And still no drug-testing program.
"So now here we are, 30 years later, toughest testing program in American sports. Even WADA [World Anti-Doping Agency], which was critical of us at one time, has raved about our program. We must be doing something right. I haven't heard from anybody in Washington in 8 1/2 years.
"And so here we have this program. It's a tough program. And the enforcement of that program must be just as tough.
"The one thing I often do is I meet with the Professional Athletic Trainers. I love that group. They know it. When I ran the Milwaukee club, I used to spend more time with the trainer than anybody else, because he knew everything that was going on. And they all tell me, 'We're doing fine. Clubhouses have never been like this.'
"But we try to be vigilant in every way. So the only thing I can say to you about the investigation is that it's thorough, it's comprehensive, and it's aggressive. I'm proud of that, and it's a tribute to what we're trying to do.
"It's one thing to say you have a tough program, but we need to enforce it well. We have a tough program. We have left no stone unturned. I think it's consistent with everything we do."
In the question-and-answer session of Selig's appearance, the Commissioner said that the timing of possible player suspensions rising from the investigation could not be guided by the pennant-race implications for individual clubs.
"We have to complete this investigation," Selig said. "I have to see the results of this investigation. Then we have to move forward. That is the only concern."
Selig commented on a wide variety of topics, including the possibility of expanded replay. Both Selig and Joe Torre, executive vice president of baseball operations, who serves on a subcommittee studying the possible expansion of replay, indicated that there would be some expansion of replay. But they said those changes would probably not be sweeping.
"We have to be careful not to upset the pace of the game," Selig said. "On the other hand, if we can make some changes that are constructive and fit in. ... We have to be careful, in our zest to improve things, not to affect the game as we've all known it."
"We're trying to make sense of what makes sense," Torre said. "We're not going to get stuck in the mud saying we're not going to do anything when technology is out there saying we can improve it somewhat."
Torre said he was hopeful that changes could be in place for the 2014 season.
Selig also expressed concern with the attendance at Tampa Bay Rays games and the lack of support for a new stadium for the Rays.
"It's very disappointing and very worrisome," Selig said. "The Tampa Bay club I believe is 2 1/2 games out [of first place in the American League East] at the All-Star break. The first thing I do every morning is look at attendance at every game. It's beyond disappointing. [The Rays] have been so competitive and have really done a marvelous job in a situation that is economically not tolerable."