The Canterbury District Health Board is carrying out a serious incident review following the unexpected death of a patient.
The health board would not provide any further information about the patient or when they died, saying the case had also been referred to the coroner.
Its chief medical officer, Sue Nightingale, said the review would ascertain the facts around the death.
She said it would identify whether changes needed to be made to systems and processes that could have prevented what she described as a sad outcome.
Any recommendations following serious incident reviews were published annually by the Health Quality and Safety Commission, Ms Nightingale said.