Ngoo helped United win the Milk Cup in Northern Ireland last week and is chasing a deal with the club's academy.
The 16 year-old stands at 6ft4 and has been likened to new Tottenham centre-forward Peter Crouch.
Luke Hobbs, Southend's academy boss, told his club's website of Ngoo: "Michael has improved so much during the last 12 months. He is effective in the air and a good finisher. Michael is a coach's dream.
"When Dean Austin watched this team play against QPR before Christmas his opinion was that Michael was very similar to Peter Crouch when Crouch was a scholar at Tottenham and Austin was a pro there. Michael is a player with so much potential. "