WHO experts and others from National Institute of Virology, Pune and a central medical team from New Delhi were visiting villages and meeting local residents to collect information about the disease, a health official told IANS on telephone.
The WHO team arrived Thursday and visited some villages, he said.
The mystery disease was identified as encephalitis by health experts Thursday. But the Bihar government is yet to officially confirm it.
"It is not a mystery disease, it is encephalitis that killed children," said I.P. Choudhary, a member of the central medical team from New Delhi.
But state Health Minister Ashwani Kumar Choubey said: "It was not proper to term it as encephalitis."
All the children died after they got high fever followed by convulsions and unconsciousness. Locals have repeatedly been terming the disease as 'chamki ki bimari', saying the symptoms were similar to those of encephalitis, which causes inflammation of the brain.
Over three dozen children are undergoing treatment in various hospitals in Muzaffarpur, Motihari and Patna.
