Dam failure
Estimates of the death toll from the Cultural Revolution, including civilians and Red Guards, vary greatly, ranging from hundreds of thousands to 20 million. The exact figure of those who were persecuted or died during the Cultural Revolution, however, may never be known, since many deaths went unreported or were actively covered up by the police or local authorities. The state of Chinese demographics records was also deplorable at the time, and the PRC has been hesitant to allow formal research into the period. In addition, the Banqiao Dam failure, considered by some as the world's greatest technological catastrophe in the 20th century, occurred in Zhumadian region of Henan province in August 1975, resulting in an estimated death toll between 85,600 to 240,000.