At least 22 students in the Indian state of Bihar are dead and dozens more are in the hospital today after eating free lunches provided by the government. Although the exact cause of the students' deaths is not yet known, the BBC reports that initial tests suggest that the food may have been tainted by organo-phosphorous, a commonly used insecticide.

The students, all under the age of 12, received free meals from the Indian government's Mid-Day Meal Scheme, which feeds 120 million children across the country every day. The surviving children displayed symptoms ranging from chest congestion and vomiting to dilated pupils.

PK Shahi, education minister for Bihar, told the BBC that the Mid-Day Meal Scheme feeds 20 million children in his state, reaching very remote village schools. That scale makes it "a challenge" to check food before it is served, he said.

The Mid-Day Meal Scheme — which got its start as a regional program nearly a century ago and went national in 1995 — provides critical nutrition to hungry students, but it has also been plagued with problems. The Wall Street Journal's IndiaRealTime blog uncovered reports of food containing lizards, snakes, cockroaches and worms and previous incidents of food poisoning and death. Studies have found that schools often lacked the ability to cook food in a hygienically safe manner and that local staff members had been poorly trained to monitor the quality of the food. In April, a government panel suggested distributing pre-packaged food that would not need to be cooked locally.

This week's deaths sparked violent protests in Bihar, with hundreds of residents of the village of Dharmasati Gandaman damaging private property and setting fire to a bus and four police cars. According to another report from the BBC, local political leaders had been chased from the streets. The riots may have stemmed from an offer to pay families of the dead children 200,000 rupees ($3,370) in compensation, which has been called "insensitive and callous," according to Hindustan Times.

It is unknown if the poison originated with the food. The school's cook, who is also in the hospital after eating a small amount of the rice from that day's meal, told PK Shahi that the school had provided a new type of cooking oil for use and she thought it looked "discolored and dodgy." According to Hindustan Times, the cook is the mother to two of the children who died.

Shahi has told the media that there will now be investigations to determine if the poisoning came from accidental tainting or if it was deliberate.

The 22 dead children were buried this morning while investigations into their deaths — and the resulting riots — continue.