http://www.news.com.au/dailytelegraph/story/0,22049,22447050-5001028,00.html
What a shitty way to die. ;)
They probably died from bacterial infection.
You don't die right away from bacterial infection. More likely it was suffocation or toxic gasses.
I was watching on TV the other day and some guy drove the porter potty things around to pick up the "waste" and anyways while he was dumping it in his one area he got too close to the stream and he got sucked into the pool of poo and drowned