Education official: We're trying to improve
Shahi, the Bihar state education minister, told CNN that 20 million children receive hot meals in about 73,000 elementary schools.
"We have been endeavoring to improve the quality and ... try to get good food served," he told CNN's Michael Holmes.
"However, the challenge is still there because the magnitude of this program is so huge that there are a number of challenges." He said those challenges are at least partly financial.
"Even though I would unhesitatingly admit that there are some quality issues before us, this is the first incident which has happened in the state," Shahi said. "In the past, we have received complaints regarding quality, but the incident of this nature ... has really shocked us -- shocked the entire state."
What was the poison?
It's unclear whether the children were intentionally or accidentally poisoned.
But officials believe the poison was an organophosphorus compound, a type of chemical that the U.S. Centers for Disease Control and Prevention says is commonly used in agriculture.
It's a nerve agent related to sarin gas, which is used in chemical warfare, the U.S. Health Department says.
Exposure to a high dose can cause an irregular heartbeat, difficulty breathing, paralysis and seizures.
Violence erupted Thursday when dozens of men reportedly attacked one of the base kitchens of the Ekta Shakti Foundation -- a non-governmental organization that supplies lunches to more than 1,200 schools in the Chhapra district of Patna.
The group's vice president, Rajnikant Pathak, told CNN the foundation had already stopped supplying meals to students Wednesday after news of the deaths.
Free meals to tackle malnutrition
A program providing one free hot meal a day to school children has proved incredibly popular as part of India's wider effort to tackle malnutrition. Children ages 6 months to 14 years get take-home rations or are provided with hot cooked food.
The wider $22 billion-a-year welfare scheme aims to sell subsidized wheat and rice to 67% of its 1.2 billion people.
According to the Indian government's figures, nearly half of India's children suffer from malnutrition of some sort.
Since a landmark Supreme Court decision in 2001, all government schools in India have been required to provide free meals to students younger than 13.