According to a notice released by the US embassy in India, from April 1, 2018, the U.S. Embassy in New Delhi will no longer process IR5, IR1, IR2, CR1, or CR2 visas. The U.S. Consulate General in Mumbai will be the only interview location if you are in process for an IR5 ( parent of a U.S. citizen), IR1/CR1 visa (spouse of a U.S. citizen) or IR2/CR2 visa (unmarried minor child of a U.S. citizen), AND your interview is scheduled on or after April 1, 2018.
If you are interview is scheduled after April 1, 2018 then your letter from the National Visa Center will specify the location of your interview, along with further details about interview preparation.
Earlier, the US Embassy in New Delhi and the US Consulate General in Mumbai both process immigrant visa applications.
According to a report by United News India, an US embassy official said there is enough space in the Mumbai office of the US consulate and also the US has single office in all the countries for issuing immigration visas. "In view of these factors the US has decided to shift visa operations to Mumbai office," the official added.
This move is bound to inconvenience the people applying for immigrant visas in the Northern states of India.