From the Daily News:

Jason Giambi failed a Major League Baseball-administered amphetamines test within the last year, which has subjected him to additional drug testing, sources told the Daily News. Giambi tacitly admitted last week that he has used steroids, but he failed to mention that he has been caught using other drugs.

Because Major League Baseball's amphetamines policy keeps a first positive test secret, however, it is unlikely Giambi will be asked about it when he meets with representatives from commissioner Bud Selig's office, possibly as soon as tomorrow on the Yankees' day off.