A building site in Dublin city centre has been closed down temporarily after more than 20 workers tested positive for Covid-19.
The site, which is operated by John Paul Construction, will see the construction of a hotel and apartments on Townsend Street.
It is understood it closed at the request of the Health Service Executive this morning.
There are 200 people working on the site, but it has not been disclosed how many of them have tested positive for the coronavirus.
This evening, Acting Chief Medical Officer, Dr Ronan Glynn said there had been over 20 cases associated with the construction site in Dublin.
He said a number of other workers from the site had been tested and were waiting for results.
Dr Glynn said this was the first significant cluster on a construction site and there was a full outbreak control team in place.
However, he said he wanted to use it to remind employers of their need to ramp up their efforts to put the safety of staff and customers first.
John Paul Construction issued a statement about the closure saying "a staff member on one of our construction sites in Dublin had tested positive for Covid-19, comprehensive testing has identified a number of additional positive cases.
"We have followed the specific advice of the HSE and the Health and Safety Authority at all times in relation to this matter and are assisting the HSE in arranging further tests as required.
"We have temporarily closed the site as advised by the HSE.
"The health, safety and well-being of those who work with us and the communities in which we operate is our top priority and we wish those affected a speedy recovery."
Speaking at the Department of Health press conference this evening, Dr Glynn said: "We are now seeing outbreaks of the virus in a range of work settings, including in construction, in fast food outlets and in supermarkets.
"We can't underestimate how quickly clusters develop. We have come so far together, but we need to stay vigilant to prevent a resurgence across the whole country in the coming weeks."
The site, which is between Townsend Street, Moss Street and Gloucester Street, is being developed for a 393-bedroom hotel, 202-aparthotel, a large ground floor restaurant and 21 apartments.
Regional Officer with Unite Tom Fitzgerald said he had concerns that construction workers at the site were not tested for Covid-19 on site.
Mr Fitzgerald told RTÉ's Drivetime that workers were sent home in the interim period between learning that one person tested positive for the viral illness and being tested.
He said he believes workers were informed that there was a positive case on site last Wednesday, and they were tested a number of days later, on Saturday.
Mr Fitzgerald reiterated his call for onsite testing for all sites currently under construction.
On the same programme Barry Murphy, Trade Union Official with the Plasterers Union Opatsi, said he had "huge concerns" that there is a "fear factor" among workers not to report potential health and safety issues surrounding Covid-19.
He said: "There is a huge fear for these workers, who have been on €350 a week, that if they do leave the site over safety concerns that their job will be gone."
Mr Murphy said employers need to guarantee that workers will not be victimised if they are fearful of going to work due to underlying health conditions.
The World Health Organization says data to date suggests 80% of Covid-19 infections are mild or asymptomatic, 15% are severe infection, requiring oxygen and 5% are critical, requiring ventilation.
Generally, you need to be 15 minutes or more in the vicinity of an infected person and within two metres of them, to be considered at-risk, or a close contact.