The prisoners complained of vomiting and diarrhoea since last night and were taken to the hospital in the prison complex today, jail Superintendent S Shanmugasundaram said.
While about 150 of them were lodged in their cells after treatment, others were under observation at the hospital, he said.
Samples of water and food had been sent for testing to ascertain the cause of the illness, he said.
Doctors and para-medical staff from Government Mohan Kumaramangalam Medical College Hospital also attended to the prisoners.