The Magpies have signed a loan deal for the youngster for a permanent move.
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The Magpies have added the striker to their academy roster on the deadline and will now try to develop the 19-year-old prospect.
A statement from United confirmed: “Santiago Muñóz has joined the club’s academy with an initial 18-month loan deal .
“The 19-year-old, who was born in the USA, comes from the Mexican first division club Santos Laguna, where he made his debut last year, scoring three goals and providing three assists in 13 league games