At a news conference after the game, Sosa said the use of the bat was a "mistake. I know that, and I'm sorry."
The world-renowned Cubs player says use of the bat was an accident. Sosa explains that this bat is one he uses for batting practice to put on a show for fans, but in this case, he grabbed the wrong bat when game time arrived.
The Cubs had runners at second and third when Sosa broke his bat with a grounder to second that at first appeared to drive in a run.
But crew chief Tim McClelland gathered with the other three umpires to examine the bat. Cubs manager Dusty Baker came out and the umpires showed the bat to him.
Mark Grudzielanek was sent back to third base, the run was wiped off the board and Sosa was ejected as he stood in the dugout.
Umpires took part of the bat into the Cubs dugout and down the runway toward their clubhouse. McClelland also was the umpire who took away a home run from Kansas City's George Brett in 1983 because of excessive pine tar, a decision later reversed by AL president Lee MacPhail.
Cork inside a wooden bat is thought to help players hit the ball farther and is against baseball rules. Several players have been caught using altered bats in the past, including Albert Belle, Wilton Guerrero, Chris Sabo, Billy Hatcher and Graig Nettles. All were suspended.
But Sosa is a far bigger star, 17th on the career list with 505 homers, and he gained international prominence in 1998 during his home-run battle with Mark McGwire.
"Deep down in my heart I truly believe Sammy didn't know that was in there," Cubs manager Dusty Baker said. "But I just hope that this event, whatever it was, doesn't tarnish his career or take away all that Sammy Sosa's done. For baseball and for Chicago."
Sosa met with the media immediately after the game, and many of his teammates watched his news conference to hear his explanation. He then came into the clubhouse to apologize, Harris said.
"Yeah, I believe him. You can only believe a man until he's proven wrong," Baker said. "In our society, you're supposed to be innocent until you're proven guilty. But things have gone the other way. You've got to prove your own innocence, it seems like. Seems like guys are guilty no matter what."
Security confiscated the corked bat so it could be turned over to major league baseball. Sosa said security officials also took the rest of his bats - filling two boxes and a canvas bat bag.
But they won't find anything illegal, he said.
"I don't really need to use that," he said.
But there will always be people who doubt him - and other players - from now on.
"Had I known there were corked bats in the bat rack, I certainly would have been using them, too. I'd have probably hit 25 home runs," said Arizona's Mark Grace, a former Cubs' star. "It's weird. Instead of hitting them 500 feet, he wants to hit them 550, I guess."
And it's not just Sosa who may suffer from the fallout.
"Everyone who hits a home run now, they're going to think you're using a corked bat," said Atlanta's Andruw Jones, who hit a game-winning, two-run homer against Texas. "It just makes home-run hitters look bad."
"Unfortunately, it's a dirty mark, when you consider all he's accomplished," Yankees manager Joe Torre said. "It's really unfortunate for the game. Everybody's scratching their heads right now. ... It's embarrassing. He's too good of a player. It's too bad."
But how can one of the game's foremost power hitters repair his reputation or silence the doubters?
"It's going to be tough. Some fans are probably not too happy about it," said Sosa. "I've got to deal with that... I know that I lost the fans and they have been great to me. It's a mistake, and I take the blame for it."
Seattle second baseman Bret Boone said Sosa's career shouldn't be judged on this one incident.
"I just hope it doesn't taint what he's done," Boone said. "Corked, not corked, he's got as much power as anyone in baseball. He's probably got as much power, outside Mark McGwire, as anyone in history. It's probably embarrassing for him... Pitchers cheat all the time. They scuff balls, use pine tar. I've never used a corked bat, not even in batting practice. If I was guaranteed I wouldn't get caught, I probably would."
Sosa just came off the disabled list last Friday after having the nail taken off his big right toe and missing 17 games.
Entering Tuesday, he was just 2-for-15 in his three games since coming off the DL, including one five-strikeout game in which he also had the game-winning single against Houston.
Sosa, a six-time All-Star who reached 500 career homers earlier this season, hasn't had a homer since May 1 and his power numbers have dropped drastically since he was beaned April 20 by the Pirates' Salomon Torres.
He has just six homers this season and 24 RBIs, while batting .285.
Sosa has the most 60-homer seasons (three) in major league history, hitting 66 in 1998, 63 in 1999 and 64 in 2001.