Leinster's Champions Cup clash with Toulon at the RDS Arena on Friday has been cancelled after the match was deemed unsafe to play.
The decision to call off the round-of-16 tie was made by the matchday medical risk assessment committee after it was told that a Toulon player who did not travel to Dublin had tested positive for coronavirus.
The French club completed an additional round of testing in the Irish capital, producing no confirmed cases, but the committee still had no option but to cancel.
"It was concluded that there were a number of high-risk contacts with the player who had tested positive and deemed the match unsafe to play with the participation of those identified contacts," a European Professional Club Rugby statement read.
"Having been notified of that position, Toulon informed EPCR that they could not select a matchday squad to safely fulfil the fixture.
"Having explored all possible alternative arrangements to facilitate the staging of the fixture, it was decided that the match could not be played safely given both the current public health guidelines in Ireland and EPCR's Covid-19 protocol."
The outcome of the game will be decided by a match result resolution committee, with a quarter-final against Exeter or Lyon awaiting the team that progresses.