A 6-month-old Kapiti girl has suffered a "severe" head injury, sparking a police probe into how the injury occurred.

The girl was airlifted to Wellington Hospital yesterday after an ambulance was called to an address in Kapiti, north of Wellington, about 4.30pm.

A Wellington Hospital spokesman said the girl remained in a critical condition in the hospital's intensive care unit this evening.

Detective Senior Sergeant Grant Ferguson said the Wellington criminal investigation bureau had launched an investigation.

Advertisement

"This little 6-month-old girl has received a severe injury to her head. We are in the process of unraveling the circumstances that have led to this injury occurring," he said.

Police have been speaking to family members who had contact with the girl yesterday.

Officers were also examining properties at Waikanae and Raumati Beach on the Kapiti Coast.