Privacy Commissioner Marie Shroff has formally launched an investigation into the blunder which saw ACC send private information about more than 6000 clients to a disgruntled claimant last year.
Ms Shroff said the investigation would also cover ACC's standards for securing personal information.
However, she also said it appeared the breach only involved ACC claims that were under review in August last year.
"If your claim was not under review at that time, it is likely that you are not affected.''
It appeared the information did not contain medical or "accident'' details, she said.
ACC has moved extra staff into call centres as tries to contact every client affected but
Ms Shroff said anyone who believed they may be affected but had not yet heard from ACC in the next two days should assume "no news is good news''
Otherwise they could call a toll free number 0800-101-996 and ask to speak to the person dealing with the privacy breach.
Claimants who wanted to complain about a breach of their privacy should go directly to ACC in the first instance.
"If they are not satisfied with ACC's response, and they believe that the breach has caused them harm, they can contact us to make a formal complaint.''
ACC chief executive Ralph Stewart yesterday confirmed reports that in last August an ACC case manager accidentally emailed a spreadsheet with information about other clients to a long-term claimant.
About 9000 records were sent relating to about 6000 individuals giving information including their names and claim numbers.
He revealed that Philip Murch, ACC's national manager of Recover Independent Services, first learned of the potential breach during a routine meeting with the claimant in December but didn't inform his superiors.
"We didn't do enough at that point,'' said Mr Stewart.
He has apologised to affected claimants.