In case you didn't see this story...
I can vouch for the general nature of the article being true; it was an Indian burial ground. In fact, I have a cousin who was working for the architecture firm for the stadium who clued me to in to this in the 1980s.
Oh and by the way, did you ever wonder why the parking area has grass strips for you to park on? That was a concession made to preserve green space in honor of the burial grounds.