Nine Hull FC players and three members of staff have tested positive for Covid-19, the Rugby Football League has announced.
The Hull club's scheduled Super League match against Castleford on Sunday was postponed after six players and two coaches tested positive in the wake of last Sunday's defeat by Salford.
That number has now gone up after further testing, with seven of the players having featured against the Red Devils.
Hull's scheduled Challenge Cup sixth-round tie against Castleford, which was due to be played next Saturday, has also been postponed.
The RFL says all the Salford players and staff have tested negative for the second time this week but 13 of them were forced into quarantine and the club's league game against Catalans Dragons on Saturday was called off.
A statement from the governing body said: "Hull FC continue to work closely with the Rugby Football League and Public Health England.
"Both the club and Rugby League Cares are providing welfare support to the players and staff affected by Covid-19."
The Red Devils have already announced two further rounds of testing next week amid calls for more stringent policing of bio-security measures to combat the coronavirus pandemic.
Former Wigan and England full-back Sam Tomkins has called for Super League to follow the lead set by the NRL, who resumed the season in May amid tight restrictions and have largely enjoyed a trouble-free run.
