A number of soccer "fans" are understood to have used forged tickets to gain admission to Finn Park for the big north-west derby clash between Finn Harps and Derry City last night.
It is believed that the forged tickets were presented at the entrance reserved for use by away fans.
It is likely that Harps may have to re-examine the type of tickets used for future big games.
There was also a problem for stewards as a significant number of fans sporting Derry City colours also watched the game from the old river end terrace.
This area has been closed for spectators in recent seasons.
However, stewards were unable to prevent several hundred spectators from using the grass banked area behind the town goal.
A number of flares were lit and thrown from this section as well. Gardai and stewards moved into remove the flares.
The matter will be investigated as a part of a post-match review of match-day arrangements.
However, there were no reports of any disturbances during the match.
A crowd in excess of 4,000 was in attendance as Harps made a winning start to their return to the Premier Division by beating their great rivals Derry City 2-1.
It was only the second time that Harps have beaten Derry in a league game.
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