Yang Ping turned to Yang Caiying, Lin Fan and others for help, Huang said.
The police said they were waiting for autopsy results to determine the cause of Jiang's death.
Jiang Weisuo, founder and general manager of Yanglinbaofeng Agriculture Science and Technology Development Company in Shaanxi, had faced great pressure after his whistleblowing in 2006.
He was called "black sheep" by his competitors in the dairy industry.
It was not till 2008, when the milk powder contamination scandal shocked the whole country, that Jiang earned himself the reputation of "hero" and "pioneer."
The melamine-tainted milk power resulted in the death of at least six babies and left 300,000 others ill in the country in 2008.
A number of Chinese officials were removed from their posts and scandal-tainted Sanlu Group, once a leading dairy producer in the country, went bankrupt following the exposure. Some members of Sanlu's management had been jailed.