Migrants from Bangladesh and neighbouring states have not only made West Bengal India's most densely populated state, but also created serious soci-economic problems, according to recent findings.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/bengal-most-densely-populated-state
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/asian-age-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/health