Santiago Munoz signed a four-year contract with Santos Laguna before making the move to Newcastle United.
Chronicle Live reports Munoz is on an 18-month loan that protects both Santos Laguna and Newcastle.
The striker joined on deadline day and will hook up with the under-23s after being impressed with the plan laid on for him by Steve Nickson.
But it's emerged he has signed a four year contract with his Mexican club, who say they will be happy to take him back if United decide not to exercise the option agreed on Wednesday.
"In the unwanted event that Santi doesn't stay at Newcastle he would come back to us," president Dante Elizalde said.
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