The gas leak occurred from a public health department pump house on the premises of the government-run hospital, said an official.
Those taken ill due to the chlorine leakage included some students of the medical college, firefighters, patients and their relatives.
"While 46 people were taken ill following the gas leak, 25 were discharged after giving them first aid. The remaining 21 people have been admitted to hospital and their condition is stable," said state Health Minister Pradeep Jena.
The district officials including the district collector have reached the hospital.