Health Minister Robin Swann said he first became aware of the seriousness of concerns around Clifton Nursing Home in north Belfast last week.
Mr Swann was speaking as health bosses face a fresh care home scandal after it emerged nine residents have died from Covid-19.
Efforts are underway to appoint a new company to run Clifton after its current owner, Runwood Homes, failed to improve infection control measures first identified last April.
It is hoped this will mean residents will not have to move to new accommodation during the current pandemic.
“We became aware of the seriousness of Clifton last week in regards to the current situation and where it deteriorated,” Mr Swann said this afternoon.
The minister said his department has been working with Clifton for some weeks, adding that discussions were underway for a new provider to take over the home.
If this goes ahead, he said residents will have a choice of whether or not to stay in the home.
The North Antrim MLA says his department took the “radical decision” to close the nursing home in conjunction with the Public Health Agency and the RQIA and denied being slow to move when concerns were raised.
Mr Swann was speaking at the Executive’s daily update on Tuesday as Northern Ireland recorded no Covid-19-related deaths in the last 24 hours for the first time since March 18.
The news followed yesterday’s announcement that the Republic of Ireland reported no further deaths as a result of the virus for the first time since the outbreak began.
Mr Swann said: “We have all been waiting for a day like this and I do believe it is a clear sign of the progress that has been made against the coronavirus.
“However, I have to emphasise a serious note of caution. There are no grounds whatsoever for complacency.
“That will be an insult to all those who have sadly lost their lives and those who are mourning them.”
Referring to the actions of Prime Minister Boris Johnson’s adviser Dominic Cummings, Mr Swann urged people to stick with the current guidance “no matter what is happening elsewhere”.
“Don’t let someone you love or someone you don’t know suffer the consequences of your actions,” he added.