Police say they're making steady progress in the homicide investigation into the death of a Canterbury baby last year.

Three-month-old Soul Turany suffered a fatal head injury in late August, a rural property near Burnham.

Senior Sergeant Darryl Sweeney says the length of the investigation doesn't imply someone won't be held to account for baby Soul's death.

"Sometimes that takes longer than other times.

"We're factual based, we work on evidence and we work away very hard on these type of cases."

Sweeney says police have a small group of persons of interest they've spoken to several times.