Is it mold? Is it toxic? Need advice on very odd mold

In my home office today I discovered a very long thread-like substance coming from the ceiling. The ceiling area was dry but there were light brown stains suggesting water damage. The odd substance was about 36 inches long, 1/4 inch in diameter and hanging from the ceiling. I placed a garbage bag around it and was able to remove it in one piece - although it broke up a bit in the garbage bag. It was the only thread and there is no external evidence of any other mold. I have been looking at websites on toxic mold and starting to panic. Any idea what this could be?