Before the second game of the World Series on Sunday, Giambi told the Chronicle, "Uh, yeah, I was," when asked if he had been subpoenaed in connection with the probe of the Bay Area Laboratory Co-Operative, or BALCO.
Giambi said he visited Burlingame, Calif.-based BALCO last fall before going on a tour of Japan with other major leaguers.
"I just asked about some vitamins and supplements and stuff like that," Giambi said. "No big deal."
BALCO, whose clients include San Francisco Giants star Barry Bonds and Romanowski, now with the Oakland Raiders, was raided in early September by agents of the Internal Revenue Service and a San Mateo County narcotics task force.
Authorities have refused to discuss the case, and the focus of the grand jury is unclear. Officials with the U.S. Anti-Doping Agency, however, have said that earlier this year, a coach sent them a used syringe containing a designer steroid and said he got the substance from BALCO founder Victor Conte.
Conte, who told The Associated Press in an e-mail that about 40 athletes have been subpoenaed in the case, has said he was not the source of the substance in the syringe, a steroid called tetrahydrogestrinone, or THG.
Conte says that BALCO analyzes blood and urine samples from athletes, and then prescribes supplements to compensate for deficiencies in vitamins and minerals.
Although many of BALCO's star clients have not commented on the burgeoning case, the agent for U.S. shot put champion Kevin Toth told The Associated Press that Toth had been subpoenaed, and sprinter Kelli White told the San Francisco Chronicle that she too has been called to the grand jury. Testimony before the panel is expected to begin this week.