There are some “areas of grave concern” within the Covid-19 testing system in Northern Ireland, the chair of Stormont’s health committee has said.
Sinn Féin’s Colm Gildernew said the committee wanted to speak with Health Minister Robin Swann about the issues.
He said there had been “serious pressures” on testing in recent weeks.
On Saturday, the highest number of people tested positive for the virus since the Department of Health rolled out its current testing model.
There were 222 positive cases and then another 176 cases confirmed on Sunday.
There have been 977 positive tests in the last seven days.
Coronavirus-related death statistics are not updated at the weekend in Northern Ireland, where the death toll recorded by the Department of Health stands at 575.
In the Republic of Ireland, the Department of Health reported 396 additional cases of Covid-19 on Sunday and no further deaths – the death toll remains at 1,792.
Of the new cases, 241 are in Dublin – which is on its second day of elevated restrictions – and 70% of the new cases are under the age of 45.
Mr Gildernew also told BBC NI’s Sunday Politics programme that investigations into the deaths of patients at two hospitals as a result of coronavirus must provide answers to the families of those who died.
On Friday, it was confirmed five more patients at Craigavon Area Hospital and Daisy Hill Hospital had died as a result of Covid-19 outbreaks.
The Southern Trust said a level three Serious Adverse Incident (SAI) investigation would be carried out into the outbreak at Daisy Hill.
An SAI into the outbreak at Craigavon Area Hospital is already under way.
“The families are entitled to know the truth but also the health service needs to learn very quickly how this has happened,” Mr Gildernew said.
He added there needed to be “rapid learning to stop further spread”.
Mr Gildernew also told the programme that Stormont’s health committee wanted to speak with the health minister over the rising case numbers and issues in the testing system.
He said there were “problems” and that he had been contacted by a family who were self-isolating after their child was tested on Thursday and are still waiting on a result.
“They have been told at times over the phone to speak to people in England, then Scotland, and when they actually got to speak to somebody here they were told that the test hadn’t been found, so those are areas of grave concern and I think they need to be addressed urgently by the minister,” he said.
Mr Gildernew also said his party would approach a full “circuit-break” lockdown with an open mind but would want to see the data supporting such a move.
It is reported a “circuit-break” lockdown is being considered by the UK government after Prime Minister Boris Johnson said the UK is “now seeing a second wave” of Covid-19.
It involves a short, sharp period of tightened restrictions for everyone to curb the spread of the virus.
“It needs to be backed with rationale and with robust planning to ensure that it can be carried out by everyone in a way that is safe,” said Mr Gildernew.
Prof Sam McConkey, from the Royal College of Surgeons in Ireland, told BBC News NI he was “sceptical” about whether a circuit-break plan was “adequate”.
“That’s only two generations of the virus cycling,” he said.
“Because you have essential workers having to travel and perhaps you have some people who are not willing to abide by the restrictions and jump the boundaries, there will inevitably be some ongoing transmission in those two weeks and it will still be there on the third week.”
Meanwhile, SDLP MLA Sinéad McLaughlin called on Economy Minister Diane Dodds to “think of a long-term plan for recovery” following the coronavirus pandemic.
Mrs Dodds is due before Stormont’s economy committee this week.
“We need to concentrate on where we have our deficits and I want to hear more of that from the minister when she comes before us on Wednesday,” she told Sunday Politics.
“I want to hear what the plan is for the skills deficit, what is the plan for our infrastructural deficits, be that around telecoms or water and sewage problems.
“We need the executive to think collectively.”
She added it would be a “absolute disaster” for businesses if Northern Ireland went back into a “full-term lockdown”.
“They’re literally hanging on by their fingernails,” she said.