The bats were tested after he was found to be using a corked bats in a game Tuesday night against the Tampa Bay Devil Rays.
Cork was found in a bat Sosa shattered during the contest on an RBI grounder. The run was taken off the board and he was ejected when the substance was found.
After the game, officials of Major League Baseball confiscated 76 of Sosa's bats and examined them Wednesday, but none were found to be illegal.
The Hall of Fame had X-rays taken of three bats Wednesday, and CT scans on two others Thursday. Conducted by a radiologist at Mary Imogene Bassett Hospital, the tests were negative.
In order to speed up the swing, players have been known to hollow out bats by drilling a hole at the top and replacing the wood with cork.
Sosa, the only player to hit 60 or more homers in a season three times, was ejected by plate umpire Tim McClelland in the first inning Tuesday. McClelland, the crew chief, picked up the bat, took it out of play and ruled Sosa out.
Sosa also faces a likely suspension from Bob Watson, the Vice President of On-Field Discipline for Major League Baseball.
Wilton Guerrero received an eight-game ban for a corked-bat incident in 1997 and was fined $1,000. Billy Hatcher also was suspended eight games, and Albert Belle and Chris Sabo each served seven-game bans for similar violations.
Sosa has claimed he only uses a corked bat in batting practice to entertain fans. On Wednesday, he admitted to making mistake and apologized.
"Sammy has been very forthcoming," said Sandy Alderson, Executive Vice President of Baseball Operations for Major League Baseball. "We think the investigation will corroborate what he told us. There's no reason to believe his explanation is not accurate."
Also, he claimed that he is being persecuted before all the facts are known.
"The media has got me out there like I'm a criminal," Sosa said. "That's something that really bothered me and hurt me as a man. I understand. Sometimes a lot of people take (my actions) the wrong way, but they compared me like I did something out of this world. It's a mistake. We are all human and we all make them. No one is perfect in this world."
"Before we get judgmental," said Cubs Manager Dusty Baker, "we have to wait and see what the verdict is."
Among the greatest power hitters ever with 505 career homers, Sosa has been dogged by questions regarding steroids and performance enhancers, but has vehemently denied those accusations.
Sosa, 34, hit the 500th homer of his career on April 4. The third-youngest player in history to reach the plateau behind only Jimmie Foxx and Willie Mays, Sosa is the first Latin player to accomplish the feat.