An 11-year-old girl was restrained, injected with anti-psychotic drugs, and placed on a mental health ward after New Zealand police mistook her for a missing woman, a report found Wednesday.

Health officials and police have scrambled to explain the mix-up, which has appalled political leaders and stoked outrage across the country.

The girl — who displayed “limited verbal ability” — was crossing a bridge in northern Hamilton city when a passing police car mistakenly identified her as a missing 20-year-old female hospital patient, the review said.

Police drove the girl to hospital, where she was admitted to an “intensive psychiatric care unit” despite one nurse suggesting she “resembled a child”.

“Patient A lives with a disability that means she was not able to tell people about herself,” said a review by the ministry of health, referring to the girl.

After refusing to take drugs offered by staff, the girl was restrained and injected with anti-psychotic medication that is “rarely administered to children”.

“Staff were working on the assumption that they were administering medication to an adult, not a child,” read the damning review of the March 9 incident.

The girl spent more than 12 hours in hospital until police realised their mistake and called her family to pick her up.

“I just wish to start by apologising to this young person and her family for the trauma and distress that was caused,” said senior health official Richard Sullivan.

“This report is a frank read. But it is necessary to make sure this doesn’t happen again.”

New Zealand Prime Minister Christopher Luxon launched an investigation last week when the incident came to light.

“That is incredibly distressing and incredibly concerning,” he said.

“As a parent you identify with what is a horrific set of circumstances. I have massive amounts of empathy for her and her family.” (AFP)

•The young girl, who the Herald understands is autistic, was administered by injection two doses of antipsychotic medication at Henry Bennett Centre at Waikato Hospital. Photo / Michael Craig