A club spokesman confirmed that Chelsea have had contact with Lisbon regarding three of the club's amateur youth players.
He added that the only junior Portuguese players now on trial at Stamford Bridge are from Felgueiras and Pedras Rubras.
Relations between Sporting Lisbon and the Blues had taken a turn for the worse as the Portuguese side made a formal complaint to FIFA.
It's being reported that three 15-year-olds, who were due to join the Portuguese club, have trained with the table-topping side - without authorisation.
Lisbon are quoted as saying Chelsea had: "tried to recruit players by ignoring the most elementary Fifa rules."
Lisbon are quoted as saying Chelsea had: "tried to recruit players by ignoring the most elementary Fifa rules."