The Garda Commissioner has said there could be up to 500 crimes that were not investigated because 999 calls were cancelled.
Drew Harris also told the Policing Authority that hundreds of people who made those calls have been contacted and engagement has been positive.
However, over 120 potential crime victims are proving difficult to contact and may have left the country.
He said in some cases calls had been cancelled because policy had not been adhered to, for example where TUSLA may not have been informed as required.
Or a callback from the initial caller may have resulted in a cancellation in a case where the gardaí themselves should have gone to the incident regardless.
The Commissioner also said that of the 203,000 calls invalidly cancelled, 23,000 were priority calls.
The Garda review was focused on domestic and sexual violence, missing persons and health cases because these could be ongoing.
Mr Harris said it was not possible to review all 200,000 calls and in many cases the incidents, such as road traffic collisions, would be completed and dealt with.
The Commissioner also said that while he had previously pointed to 'outliers’, a small number of dispatchers who would have cancelled a large number of calls, he said the review had shown the situation was more nuanced and complex.
Individuals could have been "more industrious" in opening and closing a large number of calls.
Deputy Commissioner Ann Marie Mc Mahon also told the authority that a training programme had been established for dispatchers, which covered areas such as empathy and mental health when dealing with 999 calls.
The Policing Authority has appointed a former chief inspector of police in Scotland to conduct an external preliminary examination of the adequacy of the Garda's review into the cancellation of 999 calls.
Over 300 victims have so far been contacted.
The Policing Authority has said it is very concerned about the issue and has appointed Derek Penman to independently review the Garda's work and report back to the authority.
It said today that the invalid or incorrect closure of these incidents is a serious matter because it can prevent a caller from receiving an appropriate service at that time.
It effectively prevents both the proper recording of non-crime incidents and further mandatory steps in the investigation of crimes, it added.
The Authority said it expects this phase of the review will be completed by the end of August.
Last month, Garda Commissioner Drew Harris publicly apologised to domestic violence victims who made emergency calls for help but did not receive the standard of service from gardaí that they required and to which they were entitled.
The investigation began when gardaí discovered that 999 emergency calls about domestic violence, missing persons and health concerns had been cancelled before there was a proper policing response.
They were also not recorded on the Garda's PULSE computer system and therefore there was no follow up as is the Garda policy on domestic violence.
Untrained gardaí allowed drive official cars
The Garda Commissioner has confirmed that permission to allow untrained gardaí drive official Garda cars and vans has been reintroduced.
Mr Harris told the Policing Authority that the Covid-19 pandemic had led to an enlargement of the Garda fleet with cars being hired as community support vehicles and converted into the Garda fleet.
The provision to allow Chief Superintendents to permit gardaí who are not trained as Garda drivers to drive official cars was reintroduced in March 2020 and hundreds of untrained gardaí are now driving official vehicles - 940 authorisations were made, an increase of 340.
The Commissioner accepted the situation was "not good" but said driver training had been suspended because of the pandemic and there was a plan "to get us out of it."
Assistant Commissioner Paula Hillman said there were "strict conditions" attached to these drivers.
They were not permitted to drive in emergency mode with lights and sirens, nor were they permitted to exceed the speed limit.