Manchester United players and staff were stalked by suspected food poisoning after their UEFA Europa League trip to Moldova last week.
Erik ten Hag’s team played Sheriff Tiraspol in the Moldovan capital Chisinau on Thursday night and won 2-0 thanks to goals from Jadon Sancho and Cristiano Ronaldo.
They then returned to Manchester on a private plane, but members of the party began to feel uneasy on Friday.
As many as 12 in the United camp were affected, according to The Sun, with a handful of players missing practice on Friday and others on Saturday.
According to the report, United are investigating whether the illness was the result of something they ate in Moldova or on the plane home.
United were out of action over the weekend after Sunday’s Premier League home game against Leeds United for Her Majesty Queen Elizabeth II’s funeral was postponed over stretched police resources.
It is uncertain how badly United would have been affected by the disease had the game been played at Old Trafford.
Some of the players who missed training on Friday were able to return on Saturday and all those affected were able to leave for international duty.
United’s revival under Ten Hag, who have won five of their last six games in all competitions, will be tested after the international break when they play Manchester City at the Etihad Stadium on October 2.
The following Thursday, United then face another European away game to Cyprus, where they take on Omonia Nicosia.
Victory over Sheriff was an ideal response after United lost 1-0 at home to Real Sociedad in the first group game.