Most of the additional cost were increased by project construction contractors who exaggerated their expenditures, with only 5.4 million yuan being wasted by exploration mistakes, according to the NAO.

The office also found 20.4 hectares of land illegally used without governmental permission, while another 110 hectares approved for use have been idled for years.

To date, an area of 2.1 square kilometers, or one-third of the total suffering soil erosion in the project area, has not been harnessed, said the office.