The tents set up served as a temporary camp to accommodate the floating corpses retrieved from the Yellow River. Their purpose was to identify the bodies, investigate the causes of death, and check for viruses to ascertain if any uncontrollable, highly threatening and terrifying causes of death existed.
So far, experts have concluded that there is no such threat, and although the causes of death of these floating corpses seem normal, they are actually quite abnormal. They didn't die from drowning, but from excessive blood loss. However, the blood loss was horrific, as if they had been completely drained of blood, just like being squeezed dry. What kind of killing method could achieve this?
If it were murder, the experts really couldn't think of a way that one could drain all the blood completely without leaving behind a trace. Moreover, to kill so many people all at once and then dump them in one place is ludicrous, unless the murderer was insane.