At least 21 children have died and dozens more have fallen sick after eating lunch served at their school in India’s eastern state of Bihar.

The children, who were all below the age of 10, had been served a free meal of rice and lentils at a state-run school in the village of Masrakh in Saran district, AFP reports.

Dozens of children were rushed to hospitals in the nearby town of Chhapra and the state capital, Patna, after consuming the tainted meal.

Bihar state chief minister Nitish Kumar ordered an immediate investigation into the deaths.

There are fears the death toll could rise as some of the children remain critically ill.

A doctor treating the children at a hospital in Patna said contaminated vegetable oil could have led to the poisoning, reports BBC.

“We suspect it to be poisoning caused by insecticides in vegetables or rice,” Amarjeet Sinha, a senior education official, told the BBC.

Compensation of 200,000 rupees ($3,370) was offered to the families of each of the dead.

Free meals are offered to millions of impoverished students in state-run schools across the country.

The Mid-Day Meal Scheme is also aimed at boosting school attendance, but similar incidents of food poisoning have plagued the feeding program.