The smoke was detected from the server of the Suri Sadar Hospital at around 1.30 am following which many patients fled, the district's Chief Medical Officer of Health Kartik Chandra Mondal said.
Many of the students were scared and fled from the hospital, he said, adding most of them returned later.
However, it was found that 22 of them did not return. A police complaint was lodged in connection with the incident, the CMOH said.