A Halloween attraction at Ocean Park was shut down on Saturday (Sept 16), after a 21-year-old man died inside a "haunted house".

Hong Kong police were alerted by the theme park at 2.06pm and confirmed that a man surnamed Cheung had died at Ruttonjee Hospital, the South China Morning Post reported.

Mr Matthias Li Sing Chung, Ocean Park's chief executive officer, said Mr Cheung was found unconscious five minutes after he entered the attraction.

Park medics immediately administered first aid and an ambulance was called.

Mr Cheung was the friend of a Swire Group subsidiary's employee. The theme park visit was part of an annual staff event organised by the company's staff association.

Both Ocean Park and Swire Group offered their "deepest condolences", with Mr Li saying they will address the needs of Mr Cheung's family.

The attraction, Buried Alive, involves visitors taking a slide to enter a haunted house.

An Ocean Park spokesman said Mr Cheung had entered the staff-only backstage area "by mistake".

Ms Eva Au Yeung Yee Wwah, the theme park's director of events and entertainment, said Mr Cheung was found in "a place for our staff to carry out some maintenance work".

The attraction is now closed to let the Electrical and Mechanical Services Department investigate the incident, according to SCMP.

The department believes the incident was not due to mechanical failure.

Instead, Mr Cheung was hit by "moving parts of the slide" in an area visitors were not supposed to enter.

The 4.5m-long and 2.5m-high slide was approved on Thursday after being examined by independent inspectors.

Ocean Park cannot reopen the attraction until the department lifts its suspension order.