The NRL has offered immunity to Manly officials in exchange for information that could be used as evidence against the club in its salary cap investigation.

Fairfax Media has been told the NRL's integrity unit has approached at least two current Sea Eagles officials suspected of having knowledge of undeclared player payments,and encouraged them to come clean. The officials have been told they can take advantage of a moratorium period in which penalties are waived to encourage full disclosure.

The NSW Organised Crime Squad hasn't been able to prove allegations of match-fixing as part of its own probe, but it has emerged that secret payments in breach of salary cap rules may have been made at the Sea Eagles.

The NRL's integrity unit has spoken to current and former club officials as part of its own investigations following allegations some players received secret cash top-ups in addition to their registered contracts. Several third-party agreements are also being investigated for not being at arm's length from the club or not being properly declared to head office.