Hundreds of worshippers vomited and complained of stomach ache after they ate rice and pork after mass in Ri-Bhoi district of Meghalaya state on Sunday.
Seven children are among those to have died.
Authorities say they suspect the food served to nearly 2,000 people at the Nongkya village church was stale.
"Eight people are confirmed dead and nearly 200 are in hospital," Ramesh Singh, district police chief said.
Singh said they have sent samples of the food for laboratory tests and ordered an investigation into the incident.
The sick are undergoing treatment at four hospitals in the state capital Shillong, with some said to be critical.
Most of the victims were residents of nearby villages in the largely tribal region, which is one of India's few Christian majority states.
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