(CNN) -- At least 22 schoolchildren died in northeastern India after eating free school lunches that contained a poison, a state official said.
More than 25 others have been hospitalized in Bihar state, said Education Minister P.K. Shahi, after ingesting an insecticide that was in the food.
The poison was organophosphorous, a chemical that the U.S. Centers for Disease Control and Prevention says is commonly used in agriculture.
It is 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.
Speaking on CNN's sister network CNN-IBN, district magistrate Abhijit Sinha said an inquiry into the deaths had been launched.
CNN-IBN reported that the children were between the ages of 5 and 12 and from Dharamsati, a village in Saran district, Bihar state. It said their deaths Tuesday triggered violent protests Wednesday in Chhapra, the headquarters of Saran district, and a call from politicians for a general strike.
Madhusudan Paswan, Saran's district education officer, told CNN that 31 of the affected children were sent from the local Sadar Hospital to Patna Medical College Hospital in the state capital Tuesday night.
CNN-IBN quoted Shahi as saying the deaths were a clear result of poisoning, and an investigation would determine whether the contamination was accidental or deliberate.
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.