Seems odd that they would first deny it, but then release a report acknowledging it, without knowing where it came from. In my mind that leaves two possibilities:
1. They covered something bigger up, that they were aware of, hoping that no one would notice (somehow), and are using the public prosecutor thing as a distraction, or
2. They actually weren't aware, and a facility in Russia is covering something up, so the public prosecutor thing is their way of finding out if someone's hiding something.
I guess time might tell what happened, although it sounds like (and sounded like, immediately when the news broke) that it isn't actually really all that bad.