A baby has been seriously injured in Tauranga. (File photo)

Tauranga police are investigating an incident where a 3½-week-old baby boy suffered serious injuries.

Detective Senior Sergeant Greg Turner of the Tauranga CIB said staff were investigating the Welcome Bay incident..

Police were called after the baby was taken to Tauranga Hospital on Sunday. The boy was then flown to Starship Hospital in Auckland where he remains in a serious condition.

Turner said police were working to understand exactly what had happened to the boy and a forensic examination of the Welcome Bay property had been happening on Monday.