Dorgu attended Lecce's win at Parma last night, but was not included in the matchday squad.
Lecce and United have struck terms over a fee for the young Dane, who flew to Manchester in early hours of Saturday morning.
Before then, Dorgu said farewell to Lecce's away fans at Parma and also had a word with waiting reporters at the local airport before flying to England.
Dorgu will move to United for a fee rising to €38m.