Jason Giambi (search) was excused from testifying at Thursday's congressional hearing into steroid use in baseball, but attempts by Rafael Palmeiro and Frank Thomas to avoid appearing were rejected.

Giambi does not have to come to Washington because of his involvement in the ongoing federal investigation into illegal steroid distribution, House Government Reform committee chairman Tom Davis (search) and ranking Democrat Henry Waxman said. The New York Yankees slugger testified before a grand jury in the case in 2003.

"I appeared in front of the federal grand jury a year ago. I answered every question, told the truth and cooperated fully," Giambi said in a statement released by his agent. "I appreciate that the members of the committee evaluated my situation, and I will now continue to focus on playing the best baseball I possibly can for the Yankees and our great fans."

Four people were indicted in the case, and trial dates have not yet been scheduled.

Barry Bonds (search) and Gary Sheffield (search), who also testified before the grand jury, were not among the seven current and former players subpoenaed by the committee last week.

"From the outset, we have said that we in no way wanted our inquiry to impede or complicate any ongoing investigations by law enforcement," Davis and Waxman said in a statement Tuesday. "Therefore, upon hearing today from the Justice Department that Mr. Giambi's appearance could do just that, we have decided to excuse him from testifying. All other invited witnesses, however, will be expected to comply with the subpoenas issued to them last week."

The committee accepted baseball commissioner Bud Selig's offer to testify, according to Rob Manfred, executive vice president for labor relations in the commissioner's office. Manfred also will testify along with Sandy Alderson, a baseball executive vice president who is former general manager of the Oakland Athletics, and current San Diego Padres general manager Kevin Towers.

Manfred said union head Donald Fehr will be on the same panel.

Former AL MVP Jose Canseco (search), whose recent book accuses several stars of steroid use, also will testify. Curt Schilling said Tuesday he hoped to be excused but would comply with the subpoena if he had to.

"When you get subpoenaed, you don't have a choice," he said.

It remained unclear whether Mark McGwire, Sammy Sosa, Palmeiro and Thomas would comply with their subpoenas.