A powerful insecticide killed 23 young Indian students last week, a forensic report has found.
The children died after eating a free school lunch of lentils, potatoes and rice in the Bihar region on Tuesday.
"The report has found organophospharus in oil samples collected from the school where the mid-day meal was prepared and consumed by the children," said Ravinder Kumar, a senior police officer in Bihar state capital Patna, according to AFP.
"It was observed by the scientists of the Forensic Science Laboratory that the poisonous substance in the (food) oil samples was more than five times the commercial preparation available in the market."
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The victims, aged four to 12, were buried in the playfield near the primary school that served the lunch.
Another two dozen children are still being treated in hospital.
The deaths sparked protests in the region.
Authorities are still investigating how the chemical got into the cooking oil. No arrests have been made.
The lunch was part of India's Mid-Day Meal Scheme, which feeds 120 million children - often their only meal of the day.
The plan seeks to alleviate malnutrition and boost school attendance rates.