(CNN) — At least 22 children killed. Another 24 hospitalized. All because they ate a free school lunch like millions of other Indian children do every day.
Many of the children started vomiting soon after their first bite of the rice and potatoes. Some fainted after arriving at a hospital in Bihar state on Tuesday.
But now, attention is turning to the government's accountability over the school meals and what some describe as wildly different standards across the country.
"It is just a reflection of the sort of neglect ... and these sorts of concerns in that state and states around that area," said Reetika Khera of the Indian Institute of Technology in Delhi.
"In the southern part of the country, children get not only good quality food, they also get very nutritious food," she said. "But this is not the case in Bihar."
Outraged parents are demanding to know why the students fell ill after eating the government-supplied meals on Tuesday. But they're not getting any answers from the school's headmistress, whom CNN and other news agencies have not been able to reach.
Bihar state Education Minister P.K. Shahi said the children were poisoned by an insecticide that was in the food.
Shahi said the school's cook had questioned the quality of the oil she was supposed to use, but was overruled by the school's headmistress.
"The information which has come to me indeed suggests that the headmistress was told by the cook that medium of cooking was not proper, and she suspected the quality of the oil," Shahi said. "But the headmistress rebuked her, and chastised the children, and forced them to continue the meal."
But the cook denied those claims to CNN on Thursday, saying she did not detect any unusual smell and did not notice anything suspicious with the oil.
What was the poison?
It's unclear whether the children were intentionally or accidentally poisoned.
But officials believe the poison was organophosphorus, a 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.
Anger turns into violence
The children's deaths sparked violent protests Wednesday in Chhapra, the headquarters of Saran district, and a call from politicians for a general strike, CNN sister network CNN-IBN reported.
Violence continued 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 school 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 aged 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.
Shahi said 20 million children receive hot meals in about 73,000 elementary schools.
"We have been endeavoring to improve the quality. However, the challenge is still there because the magnitude of this program is so huge that there are a number of challenges," he said.
"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 happened for the first time. It has really shocked us -- shocked the entire state."
District magistrate Abhijit Sinha said an inquiry into the deaths is underway, CNN-IBN reported.
CNN-IBN said the children were between the ages of 5 and 12 and from Dharamsati, a village in the Saran district of Bihar state.