United on Thursday announced that the unnamed players are isolating pending further tests.

A statement on the club's official website said: "Following routine testing of the first-team training group today, we have identified a small number of suspected positive cases.

"This has led to those people isolating, pending further tests.

"As a precautionary measure based on COVID protocols, we have taken the difficult decision that we will not now be able to play the friendly match against Preston North End this Saturday."

The Red Devils were held to a 2-2 draw by Premier League newcomers Brentford on Wednesday, with Anthony Elanga and Andreas Pereira on the scoresheet.

United manager Ole Gunnar Solskajer has expressed his gratitude for the backing he has been given in the transfer market, with Jadon Sancho arriving and Raphael Varane poised to complete his move to Old Trafford.

France centre-back Varane's arrival appears to be imminent, with a deal agreed in principle for a reported £42.7 million fee to secure the Real Madrid man.

Solskjaer's side are due to face Everton in their final pre-season friendly on August 7 and get their Premier League campaign under way a week later against Leeds United.