It's understood Hynes, who is the 19th man for the New South Wales Blues, which allowed him to leave camp and head back to Sharks' training to prepare for Thursday night's game against the Melbourne Storm, tested positive on a rapid antigen test this morning.
While the Sharks are yet to officially rule him out of the game, it's understood the positive test - should it be confirmed - means he will be unable to play for Cronulla on Thursday night, and will be unable to return to Blues' camp after the game ahead of Origin 3 in Brisbane on July 13.
BREAKING: Nicho Hynes positive for RAT. Sent home from Sharks training to go for PCR. Waiting for result. Was with Blues on Monday - tested negative at that point. All Blues players recorded negative tests today. @9NewsSyd @NRLonNine
— Danny Weidler (@Danny_Weidler) July 6, 2022
It's understood at this stage that all Blues players have tested negative to coronavirus tests, although daily testing will continue in the lead up to the decider.
It's unclear at this stage whether any other Sharks players may have tested positive to the virus.
It comes as Hynes spoke out on Tuesday about being "thankful" that he could play for the Sharks on Thursday evening.
"I've got an opportunity to stay here and play against the Storm first and then go up to (Origin camp) afterwards," he told reporters.
"I'm very thankful they let me do that.
"I got to be 18th man for the last two games and Jackie Wighton deserves to come back into the team somewhere.
"If that has to knock me out, then so be it."
Should Hynes miss the game against the Storm, it's likely that Braydon Trindall will come into the starting side, although Lachlan Miller, who debuted at fullback a number of weeks ago against the Gold Coast Titans, could also come in off the bench into Craig Fitzgibbon's side for the home clash.