Six Hull FC players have tested positive for coronavirus.
The Super League side lost at Salford on Sunday and the Red Devils have also had their training session cancelled on Wednesday while they await test results of their own.
Five Hull FC players involved have since recorded a positive Covid-19 test while a sixth, who was not in their matchday 17, has also tested positive.
Another is due to have a retest after an inconclusive result and all those who tested positive are now required to quarantine for 10 days until 21 August.
Two members of Hull’s coaching staff have also tested positive with Public Health England informing the club and Salford of the news on Tuesday evening.
The RFL said Salford’s routine weekly test results had not yet been received but added analysis of Sunday’s match was underway to determine how many players from each team will be required to self-isolate under test and trace procedures.
An RFL statement added: “Announcements on the impact on forthcoming Betfred Super League and Coral Challenge Cup fixtures over the next two weekends will be made as soon as possible.”