The Scottish Premier League has launched an investigation into allegations that Rangers made undisclosed payments to players.
The probe, instigated at a board meeting on Monday, comes in the wake of claims from former Rangers director Hugh Adam that some payments were not included in official contracts that were registered with the SPL.
A statement from the league read: "The SPL board has instructed an investigation into the alleged non-disclosure to the SPL of payments made by or on behalf of Rangers FC to players since 1 July 1998."
The payments allegedly left out of official contracts centre on the use of employment benefit trusts, which were the subject of a tax tribunal in January. Rangers are still awaiting the outcome of the case, regarding offshore payments made from 2001 to 2010, and which could cost the club up to £49 million.
SPL rules prohibit payments to players that are not made "in accordance with a form of contract approved by the SPL".
Chief executive Neil Doncaster would not make any prediction on how long the investigation would take.
Doncaster told Sky Sports News: "First we have to establish whether there were any payments that were made that were undisclosed at the time and, if they were, we will take that forward."
The Scottish Football Association confirmed on Friday it would investigate the allegations made by Adam.
The SFA had already launched an independent inquiry into recent events at Rangers after the club went into administration over unpaid tax bills last month, and specifically whether they broke rules regarding whether majority shareholder Craig Whyte was a "fit and proper" club official.
The news came as players awaited the outcome of talks aimed at avoiding redundancies while making monthly savings of £1 million.
Administrators continued talks with manager Ally McCoist on Monday while PFA Scotland chief executive Fraser Wishart was again at the Murray Park training complex.