PATNA, India — At least 22 children died and more than two dozen others were sick after eating a free school lunch that was tainted with insecticide, Indian officials said today.

It was not immediately clear how chemicals ended up in the food in a school in the eastern state of Bihar. One official said the food may not have been properly washed before it was cooked.

The children, between the ages of 5 and 12, fell ill Tuesday soon after eating lunch in Gandamal village in Masrakh block, 50 miles north of the state capital of Patna. School authorities immediately stopped serving the meal of rice, lentils, soybeans and potatoes as the children started vomiting.

Savita, a 12-year-old student who uses only one name, said she had a stomach ache after eating soybeans and potatoes and started vomiting.

“I don’t know what happened after that,” Savita said in an interview at Patna Medical College Hospital, where she was recovering.

The lunch, part of a popular national campaign to give at least one daily hot meal to children from poor families, was cooked in the school kitchen.

The children were rushed to a local hospital and later to Patna for treatment, said state official Abhijit Sinha.

In addition to the 22 children who died, another 25 children and the school cook were in hospital undergoing treatment, P.K. Sahi, the state education minister. Three children were in serious condition.

Authorities suspended an official in charge of the free meal scheme in the school and registered a case of criminal negligence against the school headmaster, who fled as soon as the children fell ill.

Angry villagers, joined by members of local opposition parties, closed shops and businesses near the school and overturned and burned four police vehicles.

Sahi said a preliminary investigation suggested the food contained an organophosphate used as an insecticide on rice and wheat crops. It’s believed the grain was not washed before it was served at the school, he said.