Police sources told PTI that they have recovered a suicide note jointly signed by the four girls, who consumed a poisonous fruit yesterday.
One of the girls died early today while others are undergoing treatment at the Alapuzha Medical College hospital. The students were inmates of the SAI hostel.
Police said the note mentions that "small mistakes have been blown up by them".
The incident came a day after the young athletes of the SAI centre were found to have consumed beer and were reportedly questioned by seniors. This apparently had upset them.
The water training centre at Punnamada is located in an island in the Vembanad lake.