A baby girl died after taking a suspected methadone overdose, an inquest in Gloucester has heard.
Holly Agius was found seriously ill by her mother Bonny Richards in her cot at her home in Coleford on 12 January, Gloucester Coroner's Office heard.
The inquest into the 14-month-old's death has been opened and adjourned to a date to be fixed.
Paediatric pathologist Dr Steve Wills has been unable so far to ascertain the cause of the baby's death.
She was taken to hospital but medical staff were unable to save her.
Police arrested Mrs Richards, 27, and a man aged 30, thought to be her partner, on 6 February. The pair are due to answer police bail on Thursday.
Jo Grills, of Gloucestershire Safeguarding Children's Board, said it would carry out a review into the circumstances surrounding the death.
Methadone is a liquid heroin substitute commonly prescribed to help overcome heroin addiction.
Source - http://news.bbc.co.uk/1/hi/england/gloucestershire/7919608.stm