The Professional Footballers' Association has been called in after Sheffield Wednesday failed to pay its players on time.
The PFA is understood to be offering 'advice' after the Championship's bottom club gave players only a percentage of their November salaries.
It follows a similar issue in June, which was later resolved.
The Owls are bottom of the table, seven points from safety, after a six-point deduction – reduced from an initial 12-point deficit at the start of the season – for breaching spending rules.
They have collected just three points in eight games under manager Tony Pulis, who is winless since taking over a month ago.
It is understood that the EFL is yet to be officially notified of the situation, but bosses could impose a transfer embargo, which would prevent Pulis bringing in new players in next month's transfer window.