Source: ESPN/NY Times
"It's a mildly strong to strong steroid," Dr. Gary Wadler, a professor at New York University and an expert in sports doping, told the newspaper. "Potent is the word I would use."
So, there you have it.
The first comment asks a good question: Can this be ingested accidentally?
From my very brief research, it wouldn't appear that there's a very good case for that. I am no expert, so if I'm wrong, please correct me.
From this page:
There is apparently a "cyclodextrin injectable" known as Stana-Plex that contains stanozolol, but that would be no accident.
Basically, this wouldn't appear to be an accident as best I can tell. I will try to find out more, but again if you are more knowledgable than I am (which wouldn't take much), please comment.
There is an old interview at Baseball Prospectus from 2001, in which Gary Huckaby speaks with a former MLB trainer about steroids. When asked what steroids are most common, he says, "There's a lot of Stanozolol."