Detectives investigating the death of the two-year-old girl in Dungannon on Friday have arrested a 24-year-old woman.
She has been detained on suspicion of perverting the course of justice, causing or permitting the death of a child and child cruelty.
Earlier a court extension was granted for an additional 36 hours to question the 32-year-old man arrested on suspicion of the murder.
He has been in police custody following the incident in the Park Avenue area of Dungannon on Friday afternoon.
A PSNI spokesperson said the toddler was taken to hospital by ambulance but had died a short time later.
A post-mortem examination is to be carried out to establish the cause of death.
