The reported incident followed last Sunday's 3-0 defeat against Bournemouth at Old Trafford, when United supporters voiced their anger at the players while showing their backing for head coach Michael Carrick.
Manchester United's travelling party encountered an unexpected delay on Friday after traffic problems affected their journey to Stockport station, where they were due to board an Avanti West Coast service to London.
According to The Overlap's Mike Keegan, the traffic disruption meant the train had to be held for approximately 10 minutes to allow the delegation to reach the station.
The reception on board was reportedly mixed. Carrick was cheered by passengers when he boarded, while several members of the playing squad were booed.
The contrast reflected the different reactions towards the manager and his players following the Bournemouth defeat, which intensified scrutiny of United's performances.
Carrick has retained the club's backing despite the difficult run and has publicly insisted that his relationship with the dressing room remains strong.
The manager is now preparing for Saturday's Premier League meeting with Chelsea at Stamford Bridge, where United will be looking to respond to the disappointment at Old Trafford.
The journey to London provided another indication of the frustration surrounding the club, although the reported reactions came from passengers rather than an organised demonstration by travelling supporters.