Child, Youth and Family is apologising after confidential documents were found in one of its cars sold at an Auckland auction yard.
The agency is contacting the family the files relate to, to apologise.
CYF was alerted after a woman found the documents and posted on-line comments.
She has since been visited by CYF to have the confidential papers returned.
A spokesperson says the agency sells about 500 vehicles each year.
He says these are normally cleaned thoroughly to make sure all documents are removed but this did not happen in this case.
CYF has begun looking at its procedures to see how the files were left in the car.