Daniel Wells and Gary Wilson have withdrawn from the BetVictor European Masters after testing positive for coronavirus.
The players were tested upon arrival at the behind-closed-doors event in Milton Keynes, with Elliot Slessor and David Lilley also having to pull out after coming into contact with Wilson, the World Snooker Tour said yesterday.
Michael White came into contact with Wells and has also pulled out.
All other players and officials were also tested and, as a result of the quintet's withdrawal, five players will receive byes to the next round.
World champion Ronnie O'Sullivan heads that list, with Mark Selby, David Gilbert, James Cahill and Duane Jones now also without a first-round opponent.
WST said in a statement the five affected players will "now undergo a period of self isolation and will receive the support of WST".