So the "burial site" is in a sheltered location? Unless the bodies were basically shredded, I highly doubt that you would be only finding fragments so small you need to use a sieve, which seems what the article implies. That level of decomposition speaks to a warm, wet climate, or a much older burial site. If the bones are human. It can be really hard to tell without a DNA test when the fragments get too small. Many times suspected human remains have turned out to be animal bones.
So the "burial site" is in a sheltered location? Unless the bodies were basically shredded, I highly doubt that you would be only finding fragments so small you need to use a sieve, which seems what the article implies. That level of decomposition speaks to a warm, wet climate, or a much older burial site. If the bones are human. It can be really hard to tell without a DNA test when the fragments get too small. Many times suspected human remains have turned out to be animal bones.