Fifty-four children fell ill on Tuesday after eating midday meal at a government school in Bihar's Aurangabad district, an official said.
They were admitted to a Nabinagar hospital where the condition of half a dozen was stated to be critical, the official said.
The children complained of uneasiness, followed by vomiting and diarrhoea after eating the food.
The official said some children said a lizard was found in the meal served to them at the Ghirsindhi Middle School in Aurangabad, around 150 km from Patna.
The meal samples have been collected by police for forensic examination.
In 2013, 23 students died after eating midday meal at a primary school in Saran district.
In Bihar, 16 million students get food daily under the midday meal scheme, which covers 72,000 schools across the state.