- Police are searching for the headmistress and her husband for questioning
- The cook refutes claims that she had raised concerns about the cooking oil
- At least 75 men attack a different kitchen used to prepare school meals
- Authorities believe the poison is a sarin-like nerve gas used in agriculture
Bihar, India (CNN) -- The headmistress of the Indian school where poisoned lunches killed 22 students is on the run.
Local police chief Sujit Kumar said authorities are looking for the principal, who was not named, and her husband for questioning.
The students started vomiting soon after their first bite of rice and potatoes Tuesday at the school in the northeastern state of Bihar. Some fainted.
On Thursday, 25 people remained hospitalized -- including 24 students and the school's cook, whose accounts of the incident are under scrutiny.
Was it the oil?
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 in an interview from her hospital bed. Manju Devi told CNN Thursday that she didn't detect any unusual smell and didn't notice anything suspicious with the oil.
Government standards
Now, attention is turning to government accountability over the school food program that feeds more than 100 million children -- but often with 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."
The school meal program is run by the Indian government in collaboration with state governments, Khera said.
But she said substandard food is "a reflection of a more general problem, which is the lack of political interest in these programs and -- very importantly -- the lack of accountability."
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.
Indian cook: Something wrong with oil 
A woman rests with her child at a ward housing the poisoned schoolchildren at the Patna Medical College and Hospital, in the eastern Indian state of Bihar, Wednesday, July 17. At least 22 schoolchildren died in northeastern India after eating free school lunches that contained an insecticide commonly used in agriculture. Officials are investigating whether the poisoning was accidental or deliberate. 
Books, papers and dishes are seen scattered on the floor after the incident. 
An Indian man mourns as he holds his dead daughter inside an ambulance, outside a hospital in Patna. 
The deaths triggered violent protests in Chhapra, the headquarters of Saran district. 
A grief stricken mother is consoled after the death of her son. 
Villagers gather for a funeral for children who died from the poison. Deadly school lunch in India 
20 children die after eating school lunch Exposure to a high dose can cause an irregular heartbeat, difficulty breathing, paralysis and seizures.
Anger turns into violence
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 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 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.
Quality issues
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.
In 2012: Poisoning sends 38 Mexican kindergarteners to hospital
CNN's Sumnima Udas, Harmeet Singh and Aloke Devichand reported from Bihar; Holly Yan wrote from Atlanta. CNN's Tim Hume and journalist Neha Sharma also contributed to this report.
