A cluster of Covid-19 cases has been identified in the Limavady area, the Public Health Agency has announced.
The cases are thought to be linked to a social gathering in a residential house.
The PHA said testing and contact tracing was being conducted to identify people who may be potentially infected to help prevent further spread.
A PHA spokesperson said: "Anyone who tests positive for Covid-19 in Northern Ireland will be contacted by the contact tracing team to be given advice on what to do about managing symptoms and of the need to self-isolate to prevent any wider spread of the virus.
"They will also be asked who they have been in contact with so that we can follow up with those individuals to give them advice to help prevent the further spread of infection.
"Contact tracing is an established method to help prevent the further spread of infections such as Covid-19, and we are using this approach to target potential clusters which could spark new outbreaks."
The PHA said it will continue to monitor all cases of Covid-19 and look for trends and linked cases.
It comes as the Department of Health reports there has been no further deaths and 16 positive coronavirus cases in Northern Ireland.
The death toll remains at 556 people and the total number of confirmed infections is 5,815 of those that have been tested.
There are 11 patients with Covid-19 in hospital and one person in intensive care.
There are nine active outbreaks of Covid-19 in Northern Ireland care homes.
The Department of Health has said the current R number, which predicts how many individuals on average a single infected person spreads the disease to, is between 0.5 and 1.0.
Check out our live blog below to see how Thursday's developments unfolded: