A woman and two men have been arrested on suspicion of assault after a baby girl was airlifted to hospital, where she remains in a critical condition.
The 17-month-old was rushed to hospital having suffered serious injuries yesterday.
Three people have been arrested on suspicion of assault with intent to cause grievous bodily harm.
A 25-year-old woman, 18-year-old man and a 20-year-old man remain in police custody.
A spokesperson for Durham Constabulary said: "Police were called by ambulance yesterday morning at around 10.10am to an incident involving a baby girl in the Dawdon area.
"The baby was taken via air ambulance to the Royal Victoria Infirmary in Newcastle where she remains in a critical condition."