They were found during a routine security sweep of the stadium
Manchester United have begun an investigation after two fans slept overnight at Old Trafford before Saturday's Premier League draw with Arsenal.
It is understood that they broke away from a tour on Friday and hid in the toilets.
They were found during a routine security sweep of the stadium on Saturday and did not get into the game.
Police decided to release the two individuals without charge, with the club adding that there was no risk to supporters who attended the 1-1 draw as both people had been searched and had passed through a metal detector before entering the stadium.
A Manchester United spokeswoman told Sky Sports that the two people in question "went too far" in their desire to be able to attend one of the Reds' match.