Colombia's El Pais and Spain's Marca have reported that the 26-year old Colombian international had signed a deal with the Portuguese giants despite the fact he is on loan from the Sounders.
Of the reports, Hanauer told MLSsoccer.com that Sporting had not yet signed Montero because they haven't lodged a bid meeting the players release clause.
"He is officially the property of Major League Soccer/Sounders FC until Sporting Lisbon exercise the clause that allows them to buy him outright," Hanauer wrote in an e-mail to the league's official website.
"The terms had been set at the time of the loan.
"I haven't read any of the stories and will only comment if/when we actually execute something worthy of reporting."
Since arriving at the Estadio da Luz in July 2013, Montero has scored 13 goals in 14 Primeira Liga outings to top the Portuguese league's scoring charts.
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