South Australian Police have declared a murder investigation into the death of a toddler found in a critical condition at an Adelaide home earlier in June.

Police say 17-month-old Ronan was unconscious and in a critical condition when he was taken to Adelaide’s Women’s and Children’s Hospital at about 6pm on June 7.

He died in hospital two days later.

Detective Inspector Mark McEachern said Ronan had sustained head injuries and other injuries. Police believe the injuries were caused by an assault that occurred sometime earlier on June 7.

“In the two days before Ronan was taken to hospital he was being cared for by friends who are known to his parents, at an address in Ferguson Street, Glenelg North,” Detective Inspector McEachern said.

“When he was returned to his father’s house at Ottoway at 4pm on the Wednesday, he was unable to be roused and an ambulance was called.”

Police are appealing for any information from anyone who may have seen the little boy in the days and hours before he died.

Police believe the toddler was injured sometime on the afternoon of June 7. Photos: SA Police

They are particularly keen to have information about anything involving a young child in Ferguson Street, Glenelg North, on the afternoon of Wednesday, June 7. The request includes dash cam footage from the area.

Anyone with information is asked to call Crime Stoppers on 1800 333 000 or visit crimestopperssa.com.au.