Dakhma of India, open air gravesite.

On January 19, 2003 Indian officials were venturing into the jungle after receiving several missing persons reports from a nearby city.  What they found can only be described as "disturbing".

They had discovered a "Tower of Silence" also known as a dakhma.  There are around 70,000 active members of the religion called Zoroastrianism, which dispose of their dead in this manner.  The believe the soul cannot truly be freed until it is eaten by vultures. The strange thing about this instance is that there were no animals to be found other than maggots on the bodies themselves, and that the bodies the officials were able to look at did not look like any carrion birds had been eating the bodies.
The central pit in the middle had a pool of blood in it that they estimated had to be over a foot deep and was far more than the bodies around the central circle could have produced even if they were fully drained.  The stench emanating from the central pit was overwhelming and many of the people became nauseated as soon as they neared it.
The officials had photographs of the missing persons and they could not identify any of the bodies as the people who were missing.  They also noted that many of the bodies were of people in their mid-20's to 30's, not something that is usual in these situations, however it was noted that there were no immediate signs of violence to end their lives.
The officials and a few villagers were only at the site for 45 minutes to an hour before someone accidentally kicked a bone into the center pit.  When it hit the surface of the blood, the coagulated surface broke and a gas bubble exploded up and out of the pit.  The people who were nearest the pit were immediately rushed to the hospital and quarantined for infection prevention.
The people who were quarantined became delirious within hours and the next day they became violent, trying to attack hospital staff and screaming they were infected with the blood of Ahriman (The rough equivalent to satan in Zoroastrianism.  Within three days all of the infected people had died due to fever.
Indian officials organized another trip to the dakhma in order to investigate further.  They had full hazmat gear and medical staff ready in case another incident happened like the day before.   When they arrived at the site, the bodies were all missing and the pit was completely drained of blood.  There were no traces of the bodies and attempts to analyze the DNA of the few pieces of skin and hair they found came back incomplete or were unable to be tested.
A few of the officials repelled down into the pit, where they found several grates on the ground that had pipes attached to them. The pit itself was around 60 feet deep and the stain from the blood was 8 ft up the wall.  Officials also sent samples of the blood back to the lab, and when it was tested the results were mostly inconclusive, but over 1,000 unique DNA identifiers were found.  When they tried to use sonar imaging to find out where the pipes went, they could find no evidence of the pipes anywhere outside of the central stone tower.
Since 2003, the site has been quarantined and monitored by local government officials.  The area has had no activity since that time, other than curious villagers looking to see the site.
One person I found on an online forum who is familiar with the religion speculated that the people were practicing some kind of worship of Ahriman, and the site was a profane shrine to him, and when officials found it, they moved to another location where they will not be bothered.