I saw the video showing the two officers carrying the body bag containing the remains, and you can tell by the way they're carrying it - with no effort on their part - that the remains aren't heavy, and more likely just bones.
In some respects, this points more to the remains being either Stacy or Lisa. It's been almost two years since Lisa disappeared, and a year and a half since Stacy disappeared. We wouldn't expect there to be much left.
But, with only a portion of the body/bones intact, I would expect the search by LE to take at least several days, if not more. I would think they'll put divers in the water in an effort to find more of the remains.