My opinions only, no facts here:
First, the officials obtain their initial information from the main suspect's brother. This brother happens to be in prison for a fairly long stint. We do not know if the main suspect's brother was offered a deal (shorter sentence) to talk. But we presume that he claimed certain things about who abducted Holly Bobo and these things implicated his brother (the main suspect).
Then we have the utterly-predictable "jailhouse confession" of the main suspect, where he threatens his brother for ratting on him, in the presence of other inmates. I discussed the probability of this jailhouse confession before it happened; this is why I call it utterly predictable.
Then we have the immunity agreement with this other guy (see Pearl response to reedus23 post above), who apparently does not really know where the remains are. Maybe it is just me, but does anyone get the feeling that the officials are bouncing off the walls and getting worried? None of this circus would be necessary if the officials possessed unequivocal evidence from the get-go.
I said this in my Holly Bobo timeline and I will say it again here, "a lot of people may be talking, but who is telling the truth?" Sure, the prosecutors may yet get a conviction of one or more of the detained suspects, but will the truth be served?
Remember, the current names or initials being bandied about here are not necessarily the most logical suspects from the local community. I spent hundreds of hours constructing my Holly Bobo timeline, and I "encountered" other interesting possibilities during this exercise.