Leinster's Pro14 clash with Scarlets, due to take place this weekend, has been postponed due to positive Covid-19 cases within the Welsh team's camp.
The game was due to take place this Sunday, 29 November in Llanelli, however, a small number of Scarlets players have returned positive cases of Covid-19 and others identified as close contacts are now isolating.
In a statement, Pro14 rugby confirmed the decision and that Ulster players and management, who played Scarlets last week, will all undergo testing now.
"Having considered all of the available evidence, the Pro14 Rugby Medical Advisory Group has deemed that this fixture cannot go ahead as scheduled," the statement said.
"Ulster Rugby, who played against Scarlets on Sunday, carried out routine squad testing today and will receive their results in the next 24 hours.
"Pro14 Rugby will examine potential dates in early 2021 to reschedule the game."
