Reports of children falling ill after drinking water from hand-pumps were received from at least 50 schools in across the state over the past few days.
After school children, three other - including a school principal, cook and a helper - fell ill after drinking water from hand-pump in Aurangabad district Monday.
Premchand Mishra, media in-charge of the Congress in Bihar, Monday demanded an inquiry into involvement of the BJP and RSS behind the poisoning of hand-pumps in schools across the state.
"The state government should investigate the BJP and the RSS' hands behind it," Mishra said here.
The reports come close on the heels of the July 16 tragedy in Saran district, when 23 children died after eating their mid-day meal.
The food was later found to contain a poisonous substance used to manufacture insecticide.
Water-related morbidity in children has been reported from schools in Saran, Gopalganj, Darbhanga, Sheikhpura, Siwan, Purnea, Jehanabad, Sitamarhi, Arwal, Nalanda, Madhubani, Samastipur, Muzaffarpur and West Champaran districts.
Three days ago, at least 66 children, mostly girls of Kasturba Gandhi School, were taken ill after drinking water from a handpump in Sitamarhi district.
Thirty children fell ill last Thursday after drinking water from hand-pumps in Saran and Gopalganj districts, officials said.
"The CID is probing such incidents in more than 50 schools in 14 districts of the state in the last few days," a police official said, adding that besides sealing some hand-pumps, the team was also examining whether there was an organised gang involved.
A police officer told IANS on condition of anonymity that the probe would also examine whether rumours had a role in the case.
The Forensic Science Laboratory report of water samples from the poisoned hand-pumps would be received in a day or two, an official said.
Chief Minister Nitish Kumar has asked Director General of Police Abhayanand to initiate a probe into the incidents.
Nitish Kumar reportedly told Janata Dal-United leaders that the incidents were "giving him sleepless nights".
At a public function recently, the chief minister said: "I am really worried as after the contaminated mid-day meal tragedy, reports of poison being mixed in hand-pumps at schools are now coming in from various places."
Ruling party members suspect that a plot to defame the government is being played out and that the poisoning of children is being engineered to damage the reputation of the government.