Deaths linked to coronavirus in Northern Ireland could be up to 65% higher than was thought.
An additional 31 deaths here that were associated with Covid-19 occurred in a 16-day period that were not initially included in official figures.
By April 3, there were 79 deaths here, well above the tally of 48 announced at the time.
The discrepancy emerged after the official figures were compared with more complete data held by Northern Ireland's official statistics agency.
It comes amid growing concerns of a significant underestimate in the number of fatalities.
On Tuesday, a further 10 deaths were announced, bringing the death toll here to 134.
The official tally across the UK passed 12,000, with another 778 patients with coronavirus dying in hospitals.
Experts have called for care home deaths to be included with daily updates, amid fears they are going "under the radar".
On Tuesday, the Northern Ireland Statistics and Research Agency (NISRA) pledged to publishing weekly data on deaths in non-hospital settings.
SDLP MLA Colin McGrath, who sits on Stormont's health committee, said it was clear the figures to date have not been accurate.
In Northern Ireland, the Public Health Agency (PHA) publishes an official daily bulletin of new cases and deaths linked to the virus.
Figures collated by NISRA, based on the formal process of death registration, offer a more complete picture.
These will include cases where a doctor completing the death certificate diagnosed suspected cases of Covid-19, for example, where this was based on relevant symptoms, but no test for the virus was conducted.
The PHA figures include only those testing positive for the virus within the previous 28 days.
The NISRA figures also include deaths outside hospitals.
An analysis by NISRA covers the 16-day period from Northern Ireland's first known virus death on March 18.
It states that 79 deaths occurred here between March 18 and April 3, which mentioned Covid-19 on the death certificate.
On April 3, a PHA bulletin reported 48 deaths - a difference of 31, with NISRA's figures 65% higher. A similar issue has arisen in England and Wales, when official death figures have been compared to data from the Office for National Statistics (ONS).
The ONS has said its data showed that coronavirus-related deaths in England and Wales were 50% higher than government figures.
It is possible not all deaths from the 16-day period in Northern Ireland, recorded in NISRA's bulletin published last Friday, had been formally reported to the PHA immediately.
While that will partly account for some of the additional deaths, it has been acknowledged, including by Deputy First Minister Michelle O'Neill, that the true toll is greater.
Mr McGrath said: "For several weeks, I have been questioning whether we are getting the true and proper accurate figure. I think it is obvious now that we are not, and the question has to be why?"
A PHA spokesperson said: "The Covid-19 Daily Surveillance Bulletin records deaths reported to the PHA by Health and Social Care Trusts. Deaths are recorded of patients who have died within 28 days of a positive test result, whether or not Covid-19 was the cause of death. By definition therefore, deaths where tests were not taken will not be included.
"The deaths may have taken place in a hospital setting, or in the community or a care home, but must have been reported to PHA by the Health and Social Care Trust to be included in the report.
"This reporting process allows a 'real time' daily update of trends in Covid-19 deaths within each trust area. In this pandemic, public health professionals, policy makers and the public value an up to date, daily record of the number of deaths associated with Covid-19."