Hussainsagar water was said to have been entering the Indira Park tank through a surplus weir.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/fish-die-indira-park-tank-bureaucrats-blame-hussainsagar-lake-hyderabad
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/deccan-chronicle-telangana
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/telangana
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/hussain-sagar
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-pollution
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/biological-oxygen-demand-bod