The price offered for a South Sydney win by eight points or more reportedly dropped 19 cents with a Caribbean firm in the two days before kick off against Manly last year.

The round 16 match is one of two Manly matches being placed under the microscope by NSW Police and the organised crime squad, along with the Sea Eagles' round 24 clash with Parramatta.

Police are aware of the drop in price, which opened at $1.93 with online betting giant Pinnacle before falling to $1.74, according to Fairfax Media.

No Australian licensed betting companies have reported alarming trends in the lead-up to either match, with all 21 required to alert the NRL if they have any concerns over any matches.

However Pinnacle is one of 60 other companies around the world who accept bets on the code but are not signatories to the same integrity agreements with the NRL.

The firm, based on the island of Curacao and in Malta, is also said to have higher betting limits and take more money on Australian sports than its competitors.

AAP