There is a strong possibility that Delhi's potable water has got contaminated with toxic dyes after the immersion of idols on Durga Puja last week and earlier during the Ganesh festival.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/idol-immersion-may-have-contaminated-water
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/tribune-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-pollution
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/yamuna
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/toxic-wastes
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/central-pollution-control-board-cpcb
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/ngo
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/biodegradable-waste
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/sanitary-landfill