Preston North End have apologised to fans in the Sir Tom Finney Stand for the behaviour of a group of Sheffield United supporters in the executive area of the stand.
The Blades fans had purchased a corporate package and their behaviour was a concern to home fans in the executive area and seats adjoining that part of the ground.
Little was done to curb their behaviour, with them singing and standing - doing little to hide their allegiance.
Four stewards were eventually positioned near to them but didn't have the desired affect.
There were complaints made by fans on social media after the game, one which the Blades won 1-0 thanks to David McGoldrick's 33rd minute goal.
PNE released a statement on Saturday evening which said: "Preston North End are aware of problems that occurred in the Sir Tom Finney Stand corporate areas at the weekend’s game with Sheffield United.
"The club would like to apologise to any spectators who were affected by the events that took place with a group of guests in this area.
"Investigations are already underway and the club are dealing with the matter internally."
The Blades were backed by 5,577 of their fans in the Bill Shankly Kop who were noisy and good natured.
North End return to action against Leeds United at Deepdale on Tuesday night, that game set to have another sold-out away end.