The grandfather of a nine-year-old boy has been charged with his murder.
The child has been named as Alex James Robinson from Lincoln.
Officers had been called to an address in Pennell Street in the city on Tuesday and the boy was taken by ambulance to Lincoln County Hospital but was pronounced dead a short time later.
In a statement Lincolnshire police said a post-mortem had been carried out on Christmas Eve, leading to the investigation being treated as a murder enquiry.
Stewart Greene, 64, is accused of killing his grandson Alex Robinson, and will appear at Lincoln Magistrates Court.
Police were called to a house in Pennell Street, Lincoln, on Tuesday afternoon, where it is believed Alex lived with his mother Joanne Greene and four-year-old sister Evie.
A post-mortem examination was carried out following his death.
Greene, of Louth, Lincs., was earlier said to be 'helping' police with enquiries, before being formally charged with his grandson's murder on Christmas Eve.
Alex's father John Robinson, who lives just a short distance away, paid tribute to his son, and said: "My little boy up in heaven the brightest boy shining ever xxx"