A number of theories are circulating on what would have caused such gargantuan fires in Uttarakhand, reportedly the worst the state has seen in recent times.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/uttarakhand-forest-fires-natural-or-motivated
[2] http://admin.indiaenvironmentportal.org.in/category/author/seema-sharma
[3] http://admin.indiaenvironmentportal.org.in/category/newspaper/times-india-dehradun
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/uttaranchal-uttarakhand
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/forest-fires
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/timber-smuggling
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/environmentalists
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/forests