At least 142 people have died in Indian states of Assam and Bihar since monsoon flooding began earlier this month.
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Mohammad Sana Ullah, who served in the Indian army for 30 years, is sent to a detention camp in Assam state.
The victims are mostly tea plantation workers from Golaghat and Jorhat districts of the northeastern Indian state.
The government plans to make it easier for Hindus, Buddhists and Christians to get citizenship while excluding Muslims.
Authorities say 28.9 million people out of total 32.9 million population included in final draft citizenship list.
The draft National Register of Citizens will be released on Monday amid fears tens of thousands might not be included.
Police action comes after outrage over the killing of two men on ‘child kidnapping’ rumours circulated on social media.
Mohammad Azmal Haque, who served in the Indian army for 30 years, has been asked to prove his nationality.