An insecticide container was used to cook vegetables served to children in a school in Bihar's Saran district, initial reports suggested, as the toll from Tuesday's tragedy rose to 22 with three more children battling for their lives in hospital.
As opposition parties attacked the Nitish Kumar government over alleged lapses in the running of the welfare scheme, at least 15 students fell ill after lunch at another school, this time in Madhubani, on Wednesday.
Students said a lizard tail was found in the food. All the children are reportedly out of danger.
Among the dead in Saran was the cook, who had refused to use the container but was made to by the headmistress, Meena Devi, said a student who witnessed the altercation between the two.
Two children of Meena Devi were also taken ill. She is now on the run with two other teachers.
Following the student's statement, police broke open her residential store and found stocks of food and vegetables lying together with pesticides and organic manure.
They said it seemed one of the insecticide containers may have been used to measure or store cooking oil.
Principal secretary, education, Amarjeet Sinha said preliminary investigation has shown traces of phosphate from insecticides in the cooked vegetables.
Patna Medical College Hospital superintendent Amar Kant Jha, too, said an insecticide mix in the cooking medium could have killed the children.
However, the forensic lab that collected samples is yet to submit its report.
At the Dharma Sati primary high school in Mashrakh block, angry parents defied the administration and buried 20 of the children on its grounds.
"We want people to remember this tragedy forever," said one parent.
On the streets of Chapra town, thousands of protesters ran riot. They burned down four police vehicles, blocked roads and highways and targeted government institutions. The RJD, BJP and LJP called a day-long bandh. Markets were shut and vehicles stayed off the roads.
Throwing in a sabotage angle, Bihar education minister PK Shahi said a conspiracy could not be ruled out.
In New Delhi, Union HRD minister MM Pallam Raju said his ministry had dispatched an "additional secretary to the spot for a first-hand report" while also seeking one from the state government.