The 16-year-old, who was part of the La Liga team's Cadete A side last season, had already penned terms with the Red Devils in July but has only now been awarded his international clearance.
And while United are still to officially confirm the news, Puigmal made the announcement on social media platform Instagram, posting a message accompanied by a picture of himself, club legend Andy Cole and Under-18 coach Kieran McKenna.
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