Police are investigating the "suspicious" death of a nine-year-old boy.
Officers were called to an address in Pennell Street, Lincoln, shortly before midday.
A boy was taken by ambulance to Lincoln County Hospital but was pronounced dead a short time later.
A spokesman for Lincolnshire Police said: "His death is currently being treated as suspicious and a 64-year-old man is helping police with inquiries."
Officers are carrying out inquiries at the scene and a cordon put up at the address is expected to remain in place overnight.