Bihar, India (CNN) -- In less than a week's time at two separate India schools, police said Friday, they believe that children have been poisoned by their school lunches.
At least 23 students in the southwestern coastal state of Goa were treated at a hospital after they got sick at lunch, authorities said. The students, in the third to fifth grades at St. Joseph School, have been released from treatment, Vishram Borkar, a police superintendent in Goa, told CNN.
St. Joseph School is a government-aided private institution, he said.
"We have registered a case of food poisoning," he told CNN, "and our investigation is on."
Earlier this week, 23 students died and 25 people were hospitalized from food poisoning after a school lunch in northern India's Bihar state.
There were two cooks at the Bihar school, an official told CNN. Two children of one of them -- Panna Devi -- ate the toxic food and have died, medical superintendent Amarkant Jha Amar told CNN.
Panna Devi is not receiving treatment because she didn't eat the toxic food, Amar said. She has a third child who ate the food and is improving at a hospital, the medical chief said.
The other cook, Manju Devi, is also hospitalized, along with her three children, Amar added.
Earlier, CNN-IBN had reported that two of Manju Devi's children had died.
Bihar state is one of India's poorest. Experts have said the deaths shine a light on food safety in the country and have prompted discussion on how to improve national school food programs amid news that authorities warned of safety problems with Bihar's school meal program months ago.
On Friday, authorities in Bihar announced that a new committee would be formed to strengthen food preparation in rural schools. The state's mid-day meal director, R. Lakshmanan, said village communities will also help monitor standards of meals for schoolchildren.
Deaths cause protests
The Bihar students, who authorities said were between the ages of 5 and 12, started vomiting soon after their first bite of lunch. Some fainted.
The parents of at least three children have buried their lost ones near the school -- one right in front of the building, according to CNN journalists who saw the burial mounds. An official told CNN that the parents did so out of protest.
After the Bihar tragedy, demonstrations sprang up around the area as people angrily demanded answers. One news video showed men apparently attacking a school bus with sticks. Others gathered together and held signs. Students at nearby schools refused to eat. A group that supplies lunches to schools in the Chhapra district of Patna was attacked.
It's unclear whether the children were intentionally or accidentally poisoned. An investigation is under way, and police told CNN that investigators have been unable to find the headmistress of the school in order to question her. Authorities were questioning the cook, also hospitalized in the tragedy.
Agricultural chemical suspected
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.
Bihar state Education Minister P.K. Shahi said the children were poisoned by an insecticide that was in the food. Shahi said he heard reports that the 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."
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.
Bihar state has been working "to improve the quality and ... try to get good food served," Shahi told CNN.
"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."
CNN's Harmeet Singh reported from India, and CNN's Ashley Fantz wrote in Atlanta.