The FA have not launched any formal investigation, although documents have been passed to their compliance unit.
David Davies, the FA's executive director, said: "They will be studied very carefully and any breach of the rules and regulations that they show will then be discussed as a matter of urgency."
United issued a statement saying: "All our transfer deals are approved by the board of Manchester United plc and are conducted in accordance with the FIFA and FA rules. Details of all payments involved in those deals are sent to the football authorities as required under the regulations."
Meanwhile, referee Paul Durkin admitted he should have awarded Newcastle a first-half penalty in the goalless draw against Manchester United at Old Trafford yesterday when Alan Shearer was tripped by Howard. "It happened so quick," said Durkin. "I was expecting the ball to be played upfield and I was caught quite a distance from play. I was just totally uncertain.
"I've seen it on the replays, there is contact there and Newcastle can count themselves unlucky. From where I am, unless I'm 100 per cent certain that there has been contact then I can't give the penalty - and that was the case.
"I am disappointed because we like to get the big ones right. But people need to understand it happens so quick and I've got a split second to make a decision. "
Shearer said: "We should have had a penalty and if I was playing in red I would have had one. But it's too much to ask to give Alan Shearer a penalty at the Stretford End."
