The move comes as Premier League clubs look at options to return to training grounds later this month under the Project Restart proposal, which has led to concerns being raised from four Premier League club doctors.
United are yet to set a date for when training for Ole Gunnar Solskjaer’s side will resume at their base at Carrington.
Bruno Fernandes, Fred, Victor Lindelof and Sergio Romero were among the players given permission to leave England in March after consultation with the club.
The Premier League is hopeful of resuming the current campaign in June – potentially at neutral venues behind closed doors – but the proposals are yet to receive approval from the government.
Some Premier League clubs have returned to socially distant training last month with others waiting on the government’s next lockdown restriction review which is due on May 10.
United are fifth in the Premier League table, three points behind fourth-placed Chelsea, with nine games remaining.