I agree with you that no source is "unbiased." In fact, it is well known that even if a source of information has no "bias" it is not necessarily reliable. This was been shown in studies where witnesses to vehicle accidents give contradictory reports on what happened.
That being said, there are sources that are more careful than others.
Here is what NPR is reporting:
A National Park Service official says they're still looking into it, but they suspect recent work on the electrical system is the cause. [I did not find any reference to the incident on NPS.gov.
"The outage was most likely due to work related to an ongoing project to activate a new emergency backup generator which is part of our last remaining Hurricane Sandy recovery projects," the NPS says. It added that the outage was "unplanned."