It can't be rephrased, because it's explicitly said that's exactly what happened. "Ten years ago, following the death of it's owner, the baron, low groans began to echo every night". The accidents could be written of as just that, but as was mentioned, the tunnel wasn't there yet and it's not like it would make anything outside of directly adjacent rooms audible. Do note that they weren't checking the place out during the night...If that's the real cause, then the initial statement should probably be rephrased so it doesn't sound like the issues started 10 years ago.