A cluster of Covid-19 cases discovered in Limavady can be linked to a "social gathering" in a house, the Public Health Agency (PHA) has said.
It comes as 16 people across Northern Ireland tested positive for the virus in the past 24 hours. There were no deaths in that period.
The PHA said testing and contact tracing has begun to stop further spread following the social gathering in Limavady.
"At present we can link the cases to a social gathering in a private/residential setting," the agency said.
It added: "With lockdown restrictions being eased, this type of occurrence is to be expected, which is why the Test, Trace and Protect programme is in place."
No further deaths have been recorded from coronavirus in the past 24 hours, keeping the death toll at 556.
In the past seven days 40 people have tested positive. In total 124,190 people have been tested since March and 5,815 of them have tested positive.
There are currently 11 people in hospital with suspected or confirmed coronavirus and one of those people is in ICU and being ventilated.
Care homes, meanwhile, are dealing with 22 suspected or confirmed clusters of the virus.
The Department of Health today confirmed that the reproduction, or R, rate is between 0.5 and 1 which means that for every person who has Covid-19 they infect less than one other person.
The PHA said it will continue to monitor all cases of Covid-19.
"We will not comment on individual cases as this could lead to people being identified and deter others with symptoms coming forward to be tested.
"We would ask everyone to be mindful of this risk.
"This virus has the potential to make its presence felt in any district.
"Everyone should act on the basis that it might potentially be in their neighbourhood right now.
"That's why following the public health advice on regular hand washing and maintaining a social distance of two metres remains vitally important."
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Chief medical officer Dr Michael McBride said: "Today's news underlines once again that we have to keep up our guard against Covid-19.
"Social gatherings in private residences have been an issue on both sides of the border.
"We have made important strides forward against the virus, but we must always remember that we have a long way to go.
"We face a very uncertain next few months and the very real prospect of a very challenging autumn and winter."
Health Minister Robin Swann said clusters had been anticipated.
"I would once again urge everyone across Northern Ireland to guard against complacency.
"The virus is still present in our community and must never be underestimated."
