At least 400 jawans attached to the CRPF camp at Pallipuram were taken ill due to suspected food poisoning, the police said.
They were admitted to various hospitals in the city following complaints of diarrhoea and vomiting after consuming food on Saturday, they said.
Initial investigations suggested that the jawans fell ill after consuming fish curry.
109 jawans are under observation at Trivandrum Medical College Hospital. State health minister K K Shylaja visited them at the hospital last night.