Who or what is responsible for the false figures?
Senior gardaí at the committee yesterday admitted this has yet to be established.
An investigation, led by Assistant Commissioner Michael O'Sullivan, will provide an initial report within one month and a final version within three months.
The Garda chief said those responsible could include senior management and may face sanctions.
"We will find out who was responsible for this and we will hold them to account," she said.
She admitted that gardaí may have deliberately embellished the statistics.
Garda management's handling of the controversy
Fine Gael TD Colm Brophy questioned whether it was acceptable that the scandal has been laid bare only in recent weeks - despite senior gardaí first being alerted to problems in 2014.
The Commissioner said the full scale of the issue became apparent only in 2016, prompting the force to launch a full nationwide audit.
But during the hearing, she cited the lack of senior management when she took over the force, as well as the impact of the recession.
She denied she was making excuses - but said there was a perception that the force was "data rich" and had systems that at the press of a button that could produce data.
"We can't," she added.
After coming under robust questioning from Fianna Fáil TD Jack Chambers, it was revealed that bonuses were likely to have been paid out to senior officers.
But a spokesperson for An Garda Síochána last night said there were no bonuses paid since 2008 and that there was "no indication that there were specific targets for the amount of checkpoints and/or breath tests conducted".
Medical Bureau of Road Safety
Fianna Fáil TD Jim O'Callaghan questioned why the force requested data in relation to the amount of breathalyser equipment provided only in February of this year - just days after media reports flagged potential discrepancies.
Assistant Commissioner Mick Finn was unable to state whether he had requested the information before or after the media reports.
Further Areas of policing
In her opening statement, Ms O'Sullivan indicated the issue of the falsification of records could be prevalent in areas beyond traffic.
"My fear - and my real fear - is that this falsification is not confined to traffic data," she said.
But when coming under questioning, the Commissioner failed to elaborate on such a prospect.
Keeping the Policing Authority in the dark
Ms O'Sullivan described the fact that the Policing Authority was not informed of the discrepancies much sooner as a "complete oversight".
She said the force had apologised to the authority, led by Josephine Feehily.
Deputy Commissioner John Twomey said the issue was caused as a result of an "administrative error" on his behalf. He indicated that he failed to send a letter he had written outlining the problem.