India, July 16 -- In the quiet, residential lanes in northwest Delhi's Rohini Sector 18, is an ageing community hall, its faded brick facade blending into the quaint neighbourhood. Passersby may take it for a wedding hall past its prime - a relic of municipal planning, perhaps now used for meetings by local politicians or RWA events.

A closer inspection puts such theories to rest. There's a police van outside. Officers smoke quietly in the shade. Inside, Bangladeshi nationals lie on mattresses, waiting for deportation. Whatever the hall may have been in the past, it is now a detention centre for illegal immigrants.

It's not the only one. Across Delhi - in gated colonies, buildings yet to be inaugurated, even hotels - makeshift detention...