Ulster Rugby has suspended all training following the confirmation that a number of the club's Academy squad have been identified as having contracted Covid-19.
However, it is understood that, as things stand, the IRFU does not believe the coronavirus outbreak within the Ulster squad will affect their upcoming clash with Leinster.
The Kingspan Stadium-based club issued a statement which also said that it is now assisting those players who have the virus, while also attempting to identify any close contacts the infected individuals may have had with others.
Ulster Rugby also stated that all those who have been potentially exposed to the virus have already begun to self-isolate and that this number of individuals also includes a senior player.
No specific numbers have been revealed and, in the statement, Ulster Rugby's medical director Doctor Michael Webb said that "multiple Academy players" had tested positive for coronavirus.
With Ulster due to meet Leinster at the Aviva Stadium on Saturday evening for only their second game back since last February - they lost their opening game to Connacht on Sunday - this development could potentially put this weekend's game in jeopardy.
However, on Wednesday night the IRFU remained confident that this weekend's Irish PRO14 derbies will go ahead as planned.
Ulster are also due to travel to Edinburgh for a PRO14 semi-final clash on September 5, with their rescheduled European Champions Cup quarter-final due to be played at Toulouse on September 20.
The Public Health Agency has been informed of the developments and contact tracing has begun in line with health advice.
All four provinces underwent routine PCR (polymerase chain reaction) testing for Covid-19 on Wednesday as part of the IRFU's return to play protocols.
The results of this are due out on Thursday and, as such, are in line with the current processes from previous rounds of testing.
Ulster Rugby added: "As soon as the cases were identified Ulster Rugby immediately stood down all training of both the Academy and senior squads and sought to identify any potential close contacts.
"All individuals potentially exposed to the virus have already commenced self-isolating.
"Given this is a confidential health matter for the individuals involved, Ulster Rugby will not be making any further comment at this stage."
Dr Webb was quoted in the statement as saying: "Following confirmation of multiple Academy players testing positive for Covid-19, we are closely following public health advice in line with the IRFU's return to play protocols.
"As a result, we have taken a number of precautionary measures as we await the results of further testing.
"We are supporting the individuals involved and all will continue to be medically monitored.
"Our top priority is to ensure the health and safety of our players and staff, and we will continue to work closely with both the IRFU and PHA as we look to make a safe and measured return to rugby."