Police have named Sophie Jones aged two following her death on Tuesday night.
A post Mortem Examination has been completed however it has not ascertained the cause of death, therefore Toxicology tests will now be carried out.
Police have been granted 36 more hours to question the 29 year old woman and 41 year old man who have been arrested on suspicion of manslaughter.
Police received a call from the ambulance service following reports that a toddler had suffered cardiac arrest, at an address on Jameson Street in Blackpool.
Sadly the child who has not yet been named was rushed to hospital where she died.
A post mortem examination is due to be carried out to try to establish the exact cause of death.