A case of unnatural death has been registered, police said.

A boy drowned during swimming lessons at College Square pool in northern part of Kolkata on Sunday, police said.

The 17-year old boy, identified as Md Shahbaz, drowned in the pool during the training session, a police officer said.

A case of unnatural death has been registered, police said.

Kolkata Municipal Corporation (KMC) authorities have ordered that the swimming pool will remain closed till investigation into death of the teenager is completed.

"We are examining how the incident happened. The pool will remain closed till the investigation is over," KMC mayor-in-council Debasish Kumar said.

The swimming pool authorities claimed that Shahbaz had sneaked into a large pool, meant for trained swimmers, without the knowledge of the trainers.

His body was recovered by divers of the disaster management group of the city police.