A teenager who went to celebrate a friend’s birthday at Nicco Park fell sick while standing under an artificial waterfall and was later declared dead at a hospital on Wednesday afternoon.

Rahul Das, 18, a resident of Ultadanga, had gone with friends who told park officials that their friend had a “blackout” before he passed away.

Rahul and six friends were at the “Niagara Falls” — an artificial waterfall at the park named after the waterfall on the US-Canada border — when he fell sick.

The group was standing on a balcony attached to a steep artificial rock-like structure from which water streams down, giving guests a waterfall-like experience.

Nicco Park officials said they were alerted to the boy's illness shortly after 1pm. Rahul was given first aid before being rushed to Calcutta Heart Clinic and Hospital, officials said.

“The balcony is 15–16 feet above the ground. A flight of stairs leads to this balcony, which even elderly people can easily mount. The water falls over the shoulders of visitors, giving them a soothing experience,” said Rajesh Raisinghi, MD and CEO, Nicco Park.

“Like other visitors, a group of young boys and girls came to enjoy themselves. A lifeguard spotted that some of them were helping another boy come down from the floor where people stand and enjoy the waterfall. The boy was unconscious. We gave him first aid immediately. The nurse who gave the first aid said his pulse was weak and that we should take him to hospital," Raisinghi added.

Rahul was taken out of the water park in a wheelchair with his friends around him. He was taken to a nearby hospital in a Nicco Park ambulance, where he was declared dead.

“By the time he was brought here, he was no more. There was no sign of life. The ECG line was straight. As per protocol, we tried to revive him, but he was no more,” said Nupur Banerjee, chief medical officer of the hospital.

There were no injury marks on Rahul except on one leg, she added.

Police sources said the preliminary investigation did not suggest foul play.

“We contacted the family of the youth and informed them about the incident. The body has been sent for post-mortem. The cause of death would be clear after the post-mortem,” said deputy commissioner (Bidhannagar), Bidhannagar city police, Aneesh Sarkar.

Rahul's friends are being questioned to determine the sequence of events, police sources said.

“We are trying to find out what the group ate, and if the boy had complained of any illnesses earlier,” said an officer of Bidhannagar city police.

The police will ask his family about his medical history.

Cops are analysing CCTV footage from the park. An unnatural death case has been started.

The boy's parents came to the hospital in the afternoon but refused to talk.

Thousands — young and old — visit Nicco Park every day to enjoy rides, some of them tagged “unfit” for the elderly or for people with specific medical conditions. The waterfall is “suitable” even for the elderly, a park official said.

“We keep an eye on guests. We have lifeguards,” he added.