South Wales Police are investigating the unexplained death of a 41-year-old man at a flat in Herbert Street, Pontardawe, on Friday, June 6.
Two women aged 27 and 38, and a 27-year-old man, are currently in custody helping police with enquiries.
Anyone with information about the incident is asked to contact South Wales Police on 101 or Crimestoppers anonymously on 0800 555 111 quoting occurrence number 1400198040.