The four girls were rowers and participating in a training camp at the Sports Authority of India (SAI) Water Sports Centre in Alappuzha.

They were found unconscious on Wednesday evening at the women's hostel in the institute. The youngest, a 15-year-old national gold medalist, died last night. The other three are on pacemakers.

The four allegedly signed a suicide note before taking the fruit "Cerbera Odollam" from what is commonly known as the "suicide tree." Only one of them is conscious; she has given a statement to the police.

"There is no antidote to this poison. At this point we can only hope and pray," said Injeti Srinivas, the Director General of SAI, describing the incident as "the most tragic and shocking" in three decades of SAI.

The girls' families allege that they were "unable to bear physical and mental torture" by their seniors. "My daughter called on Wednesday morning, cried and said seniors were harassing her," said the mother of one the girls who survived.

The girls were allegedly beaten with oars and humiliated. Their relatives say coaches in the institute are notoriously harsh and there have been many complaints in the past.

Sports Minister Sarbananda Sonowal has ordered an inquiry into allegations of harassment and torture. "Strictest action will be taken if anyone from SAI is found guilty of wrongdoing. The girl who died was a very promising sportsperson. It is a big loss," he said.

An institute official denied that the girls were harassed.

One report suggests that a day before the incident, the girls were reprimanded for drinking beer. The police are investigating whether the suicide pact was linked to that.