A 12-year-old member of all-girl idol singing group 3B Junior fell into a coma after inhaling helium, Japan Today reported.
The incident on Jan 28 occurred during a recording of the programme 3B Junior Stardust Shoji for TV Asahi. The girl fell unconscious after inhaling helium as part of a game, officials said during a press conference on Feb 4.
Reports said she was rushed to a Tokyo hospital but did not regain consciousness until a day later.
She now reportedly has limited movement and cannot yet speak clearly.
Inhaling helium typically alters a person's voice, turning it high-pitched and comical.
The girl is believed to have suffered an air embolism, losing consciousness as a result of air bubbles blocking the flow of blood to the brain, Japan Today reported. The container of helium gas apparently had a sticker on it, saying "For adult use only." The network said safety precautions were inadequate.
TV Asahi has apologised to the girl, her family, and others involved in the incident. TV Asahi officials said other members of the idol group - who are all under 18 years old - had also inhaled helium gas to change their voices. No one else was injured in the incident.