A woman was arrested on Monday after a 47-year-old man and his 85-year-old mother were found dead in a flat on Cheung Sha Wan Road.

Police said they received a report shortly before 4pm that a man was thought to have collapsed in a unit at Hang Moon Building.

Firefighters broke into the flat and found the bodies of the man and his elderly mother.

Sources at the scene said the man had Down syndrome, and the suspect is his elder sister who has a history of mental illness.

Police have classified the case as murder.