Rooney suffered an ankle injury in a training-ground accident a fortnight ago and was immediately ruled out for four weeks by manager Sir Alex Ferguson.
However, reports emerged overnight that the 22-year-old had been given the green light to start training again - way ahead of schedule.
The news has come as a surprise to United officials, who felt Rooney was still some way off a comeback.
And sources inside Old Trafford have confirmed Rooney is still undergoing treatment and has not resumed training.