Word of caution using this sentence. This morning, a native speaker broke her glass, spilling juice. She apologized to everyone, and I said this sentence. A hush came over the small group. I asked, "What did I say? I was trying to say this was just an accident." As best I could understand them, they said that for something like that, "tai nạn" was considered "bad luck" and the word is used more for things like car accidents. These people came from Central Vietnam. Can other native speaker weigh in to clarify, confirm or dispute?
Edit: this would seem to fit with wordgeek comment below.