Patna, July 20 (IANS) Cooking oil with strains of toxic insecticide compound organophosphorus was used for making food at a Bihar primary school where 23 children died after a free meal, police said Saturday, citing a forensic report.

"The Forensic Science Laboratory report has found organophosphorus in oil samples collected from the school where the mid-day meal was prepared and consumed by the children in Saran district. The compound is used in farm insecticides," Additional Director General of Police (Headquarters) Ravinder Kumar told reporters here.

Ravinder Kumar said strains of Monocrotophos, an organophosphate insecticide, were present in the food. "It is highly toxic."

"It was also observed by the scientists of the FSL that the poisonous substance in oil samples was more than five times the commercial preparation available in the market," he said.

The official said the forensic evidence collected from the school was analysed at FSL here.

He said that it was a matter of investigation that how and from where this poisonous substance got mixed in the oil.

"I will not go into the details as FSL report will help the ongoing investigation into the mid day meal tragedy," he said.

According to a Saran district official, the forensic experts collected samples of the oil used to cook the meal late Tuesday night. "The oil samples had a bad odour," officials said.

Amarjeet Sinha, principal secretary, education, earlier said preliminary findings pointed to insecticide poisoning of the oil and vegetables used in the meal.

The post-mortem of the children confirmed presence of a poisonous substance in the potato-soyabean curry served to them .

Soon after the deaths, a top government official said that he suspected it could be organo-phosphorous poisoning caused due to traces of insecticides in vegetables. He added that doctors had told him that atropine had a positive effect on the affected children.

He also did not rule out contamination of the oil used to prepare the curry consumed by children Tuesday in the school in Gandaman village of the district, 80 km from Patna.

Chandrasekhar Singh, a doctor in a government hospital in Saran, who treated several children said 10 kids, who did not eat the curry, are safe. "As many as 55 of 65 children fell ill after having the curry and some died," he said.

According to district officials, the meal consisted of rice, pulses and the curry.

Parents of several children told officials that their children fell ill due to poisonous vegetable. "Some children, who consumed only rice and pulses, did not fall ill," they said.

A government inquiry report has blamed Meena Devi, absconding principal of the government primary school, for the deaths.

"There is no trace of her. The administration has decided to attach her property to put pressure on her to come forward," Saran Superintendent of Police Sujit Kumar said.

According to district officials probing the incident, Meena Devi had forced the cook to use the "toxic" oil despite the latter's complaint that it had a pungent smell.