The department heads just learn of what is happening. They cannot say "we didn't do anything wrong!!!" without investigation because it will make the university in a very negative light (it is a serious ramifications). They need to get all the facts and knowing how it happens and who is responsible for this. So this way they can make a concise action and they will make a proper statement. They are taking "investigation first and comment after" cautiously and seriously.
It's a bit unclear who complained to whom about this - and I'd expect looking into this to be part of the review. i.e. I could easily see "some people reached out to IRB concerned about lack of its involvement, IRB talked to researcher and went through process, came to result for whatever reasons" happening and not being something that is reported up the chain, because it was "resolved".
