Coronavirus testing has been significantly ramped up in Northern Ireland and community surveillance testing was now possible, the chief medical officer has said.
Dr Michael McBride said testing people in GP practices would provide information on how "the virus is behaving on the ground".
He said those admitted to hospital and care homes were also now being tested.
Another 20 people have died with coronavirus in Northern Ireland.
That brings the total number of deaths to 329, although this figure, which relates mainly to hospital fatalities, is likely to rise.
In the Republic of Ireland, 59 more people have died, with the number of deaths there now standing at 1,159.
'Break the cycle'
Dr Mc Bride said testing has begun in 13 GP practices in Belfast and will be rolled out to another 26 across Northern Ireland.
Figures released by the department on Tuesday showed that 23,376 individuals had been tested, an increase of 807 on the previous day.
Speaking at the daily press conference, Dr McBride said it was not yet time to relax social distancing and measures to ensure "we break the cycle and chain of infections".
Health Minister Robin Swann revealed that the number of Covid-19 patients in intensive care had dropped to 34 from 59 in three weeks, but said the situation remained "on a knife edge".
"Don't let anyone say this has all been overblown because, believe me, it hasn't," he said.
Mr Swann confirmed the Northern Ireland Executive was discussing the use of face masks to help prevent the spread of coronavirus when lockdown is eased.
But he said that there was a concern they might lead to a "false sense of security".
Dr McBride said there was limited evidence "some face covering may be of benefit" in enclosed spaces.
But he said this benefit was considered "marginal".
Dr McBride said good hygiene practices and social distancing were essential.
The Public Health Agency has also confirmed outbreaks of the virus in 69 care homes.
Earlier on Tuesday, the public joined politicians and hospital workers in observing a minute's silence to remember the key workers who have died with coronavirus.
More than 100 healthcare staff have died with the virus across the UK, as have many transport and other key workers.
Analysis: A stark reminder
By Marie-Louise Connolly, BBC News NI Health Correspondent
One question we are all asking is when might the restrictions on lockdown be relaxed ?
Judging from today's briefing at Stormont the shutters don't appear to be going up anytime soon.
That figure of 20 deaths gave us all a jolt and according to the health minister and the chief medical officer it is a stark reminder NI is still very much in the pandemic.
However for the first time we heard that the R value - that's the number which indicates how many people can be infected by one person - has fallen to below one. At the start of all this it was R3.
That means the risk is reducing and when it gets close to zero that should trigger the executive looking at how NI can start thinking about moving forward and raising those shutters even by a little.
Across Northern Ireland, people stopped their daily routine to reflect on the lives lost.
In the assembly chamber, MLAs halted business to observe the silence.
The first and deputy first ministers were both at South Tyrone Hospital in Dungannon where they stood with staff outside.
The son of a doctor who died in London has called on the government to issue a public apology for issues with personal protective equipment (PPE).
Earlier on Tuesday, the PSNI and Department of Health issued a joint statement expressing "deep concern" that the the lockdown regulations were being undermined by an ongoing debate on the issue of people travelling by car for exercise.
They said it could encourage some people to ignore health advice "with potentially devastating consequences".
Their overriding priority was the protection of life, they said, adding that the regulations were never going to cover all aspects of behaviour.
Other developments on Tuesday:
- Trading Standards has issued a number of enforcement notices to traders engaged in profiteering during the coronavirus outbreak
- Charities "will face a time of reckoning" after the coronavirus crisis, according to the NI Council for Voluntary Action (NICVA).
- The Health and Safety Executive for Northern Ireland has been investigating hundreds of complaints about workplace safety during the Covid-19 crisis.