Manny Ramirez and David Ortiz were among the 104 major league players listed as having tested positive for performance-enhancing substances in 2003, lawyers with knowledge of the results told The New York Times.
The two were key members of the Boston Red Sox World Series championship teams in 2004 and 2007.
The lawyers did not name the substances for which Ramirez and Ortiz tested positive, the Times reported.
One team official told ESPN.com's Amy K. Nelson before the Red Sox's 8-5 win over the A's at Fenway Park that he had "no idea whatsoever" that both Ortiz and Ramirez were on the list, adding that the team has been relatively controversy-free this year.
"At least [manager Terry Francona's] at the helm in the clubhouse and he's a magician at keeping the guys focused," the team official said.
Ortiz, after his 2-for-3 performance that included a three-run homer in the seventh inning that gave the Red Sox the lead for good, issued a statement.
"Today I was informed by a reporter that I was on the 2003 list of MLB players to test positive for performance-enhancing substances. This happened right before our game, and the news blindsided me.
"I want to talk about this situation and I will as soon as I have more answers. In the meantime I want to let you know how I am approaching this situation. One, I have already contacted the Players Association to confirm if this report is true. I have just been told that the report is true. Based on the way I have lived my life, I am surprised to learn I tested positive.
"Two, I will find out what I tested positive for. And, three, based on whatever I learn, I will share this information with my club and the public. You know me -- I will not hide and I will not make excuses."
Francona, who guided Boston to those two titles, said the news "blindsided everybody," including Ortiz.
"Nobody condones the use of performance-enhancing drugs ... the testing procedure was confidential. I don't know how you can go back on that now," he said.
Los Angeles Angels center fielder Torii Hunter, a longtime friend of Ortiz's, said he was shocked by the report.
"This hurts, this really hurts," Hunter told ESPN.com. "I don't know what to think about this. I guess you just never know what people do in the dark.
"I still love him but at the same time it's tough to hear that. I know it's going to be tough on him and tough on his family once this gets out. It's Big Papi, man, it's the Big Dog of Boston and he helped win two World Series with those guys, with the clutch hits. And now all those things are going to be tainted."
Ramirez, now with the Los Angeles Dodgers, did not address the Times report as he prepared for the Dodgers' Thursday night game against the Cardinals in St. Louis.
"You guys want to talk about the game, what is happening now, we can sit down and talk for two hours," Ramirez said. "If you want more information, call the union."
Ramirez said he found out about the report on television while flipping channels in his hotel room. He told ESPN that he shrugged, and kept flipping channels.
"Me and David, we're like two mountains," Ramirez said. "We're going to keep doing good no matter what ... Only God is going to be able to move those two mountains."
Ramirez recently came off a 50-game suspension for violating baseball's drug policy. The specific violation was never announced, but sources have told ESPN that testing during spring training this year revealed elevated levels of testosterone that had come from an artificial source.
Sources told ESPN that Ramirez was suspended because Major League Baseball had documentation to prove he had used hCG, or human chorionic gonadotropin, a female fertility drug that is used to restart a body's natural testosterone production as it comes off a steroid cycle.
In June, he Times reported Sammy Sosa was on the 2003 list. In February, SI.com reported that Alex Rodriguez was on the list, and subsequently, Rodriguez acknowledged having used banned substances from 2001 to 2003, when he was with the Texas Rangers.
"Can somebody in baseball -- we're all begging, people -- get that stupid list out and move on," Chicago White Sox manager Ozzie Guillen said. "This is ridiculous; this is embarrassing; this is a joke. Whoever is there is there, get them out, and that's it."
Players were tested in 2003 as part of Major League Baseball's survey to determine if it was necessary to impose mandatory random drug testing in 2004. There were no penalties for a positive test in 2003.
As part of the drug agreement between the union and MLB, the results of the testing of 1,198 players also were meant to be anonymous. Penalties began in 2004 and suspensions for a first positive test started in 2005.
Government agents initially obtained search warrants in 2004 for the drug-testing records of 10 players as part of their BALCO investigation that led to Barry Bonds' perjury indictment, but they found the more expansive list on a spreadsheet, obtained additional warrants and seized the larger group of records.
The case over the legality of the search is mired in the court system and eventually could reach the U.S. Supreme Court.
The Times reported the revelations about Ramirez and Ortiz came from multiple lawyers and other sources associated with the case pending.
"Today The New York Times, once again, reports what it asserts to be information contained in documents under court seal. And precisely for that reason, the [MLB] Players Association will not, indeed cannot, comment on whether the information is accurate," union chief Donald Fehr said.
Major League Baseball declined to comment on the Times' report, telling The Associated Press it didn't have the list of players who tested positive in 2003.
Hunter told ESPN.com: "Whoever got that list is just playing with Major League Baseball right now. Either put [the list] away, or just put it out. It was anonymous and now the names are leaking and it's a joke."
In February, shortly after Rodriguez confessed to using banned substances, Ortiz said publicly that players who tested positive for a substance that was banned at the time should be suspended for an entire year.
Once one of the most feared, clutch hitters in the league, Ortiz has struggled of late. After totaling 177 homers from 2004 to 2007, he did not hit his first homer this season until May 20. He played in only 109 games in 2008 because of wrist injuries.
"He's still my boy, no matter what," Hunter said. "David is a great person and I love him to death. Nothing going to change between us. I'm just shocked just like everybody else, that's all."
Information from ESPN.com's Amy K. Nelson and The Associated Press was used in this report.