The Press Association confirmed there would be an investigation into the Portuguese coach's conduct:
Per Tom Kershaw of The Independent, after watching his side recover from two goals down to win the match 3-2, Mourinho is alleged to have been caught on camera swearing.
The big win for Mourinho came a day after it was reported by David McDonnell of the Daily Mirror that the Portuguese would be given his marching orders by the club regardless of the result Saturday.
After United found themselves 2-0 down against Newcastle, the Red Devils boss would've been fearing the worst, although goals from Juan Mata, Anthony Martial and a last-gasp winner from Alexis Sanchez saw the team stage a memorable turnaround.
When the final whistle blew, the pitchside cameras naturally focused on the United boss, and he could clearly be seen muttering something after shaking hands with Magpies boss Rafael Benitez as well as pointing his little finger towards the camera.
According to the MailOnline, Mourinho's words were expletive:
After the match, the United manager said that the treatment he has received at times has been unfair.
"As a friend of mine was saying to me this morning, if tomorrow it rains in London it is my fault," he said to the press after the win, per BBC Sport. "If there are some difficulties with the agreements of Brexit, it is my fault. I have to be ready for all of this. I think a lot of wickedness and clear man-hunting in football is too much."
While United have not pulled the plug on the Portuguese yet, there will be big tests to come for the Red Devils on the other side of the international break.
Aidan Walsh provided the rundown of the challenging series of matches the team will face, starting with a trip to Mourinho's former club Chelsea:
Mourinho will hope the charge passes before that fixture. According to BBC Sport, the FA will assess footage and get a translation of what the coach said.
United currently sit in eighth position in the Premier League table, seven points back on joint leaders Manchester City, Liverpool and Chelsea.