A nine-year-old boy has died in hospital after he was found collapsed at home.
West Midlands Police said they were called to an address in Tyburn Road, Birmingham, at 5.45pm on Monday, where the boy was discovered.
He was taken to Birmingham Children's Hospital but died the following day.
Detective Inspector David Wallbank said: "We are working closely with specialists from the health services, children's services and the Birmingham Safeguarding Children Board to fully investigate the circumstances of this tragic death."
The coroner has been informed.
A West Midlands Ambulance Service spokesman said: "We were called to an address in Tyburn Road, Birmingham, to a suspected cardiac arrest.
"The patient, a boy, was taken to Birmingham Children's Hospital, drugs were administered, and CPR and resuscitation was carried out en-route.
"Birmingham Children's was pre-alerted to his arrival and he was handed over to clinicians at the hospital."
A Birmingham Safeguarding Children Board spokesman said: "The BSCB will review the circumstances of this case."