England's players were racially abused during their second Test victory over Argentina in San Juan on 12 July.
Team officials lodged a complaint to governing body World Rugby over the incident that occurred when the visitors' replacements were warming up in the first half.
England's seven replacements for the match were Curtis Langdon, Beven Rodd, Asher Opoku-Fordjour, Chandler Cunningham-South, Guy Pepper, Alex Dombrandt, Jack van Poortvliet and Cadan Murley.
"While it is clear that an incident took place, we regret that the individuals responsible could not be identified," said World Rugby, adding their investigation included witness statements and video analysis.
"Intense efforts were made to identify the small group of five or seven individuals responsible within a crowd of over 20,000 spectators," said Gabriel Travaglini, president of the Union Argentina de Rugby (UAR).
"Unfortunately, despite an exhaustive search, it was not possible to identify the perpetrators.
"We strongly condemn all acts of racism and stand in solidarity with the England rugby players who felt aggrieved."
He added that the UAR would work with World Rugby to educate fans.
