A 25-year-old woman has been arrested following the death of a 20-month-old in Mansfield.
Nottinghamshire Police said officers were called just after 6.30am on Friday to a report of concerns for the welfare of a child at a house in Wharmby Avenue.
The child was taken to hospital for treatment but pronounced dead a short time later.
The force said the woman remained in police custody on Saturday and detectives and crime scene investigators were continuing their inquiries at the scene.
Detective Chief Inspector Rob Routledge, who is leading the investigation, said: “Any death of a child is a tragic incident and I understand the concern this will cause within the local community.”
He added: “I would encourage anyone with any information to come forward as soon as possible as any information – no matter how small it may seem – could assist our officers.”
Anyone with any information is asked to call Nottinghamshire Police on 101, quoting incident number 97 of March 6, 2020.