United issued a statement saying: "Following routine tests of the first-team team training group today (Thursday), I have identified a few suspected positive cases. "This has led those people to isolate, pending further testing. "As a precautionary measure, based on COVID protocols we have made the difficult decision not to play the friendly match against Preston North End next Saturday, July 31. "We are sorry for the inconvenience caused to Preston North End fans and for any disappointment caused. Manchester United supporters who purchased tickets to the game will automatically be refunded. "At the moment, we don't expect any disruptions around our upcoming matches, but will continue to adhere to Premier League protocols in this respect."