People have been queuing across the Indian state of Assam to check if their name is on the National Register of Citizens.
India has published the final version of a list which effectively strips about 1.9 million people in the north-eastern state of their citizenship.
Families have been required to provide documentation to show their lineage, with those who cannot prove their citizenship deemed illegal foreigners.
India says the process is needed to identify illegal Bangladeshi migrants.
The BBC's South Asia correspondent Rajini Vaidyanathan has been to the village of Katajhar to meet some of the people who say they are at risk.