England lodged an official complaint with World Rugby after their players suffered racist abuse from spectators during their win over Argentina in San Juan on July 12, but the perpetrators could not be identified, the global governing body said on Monday.
The RFU made the complaint on July 15, World Rugby said in a statement, adding that an immediate investigation was launched involving witness statements and video analysis.
"While it is clear that an incident took place, we regret that the individuals responsible could not be identified," World Rugby said.
"There is no place in rugby or society for discrimination, abuse or hate speech, and any complaint of discrimination is taken extremely seriously by World Rugby."
World Rugby chair Brett Robinson condemned the incident.
"We offer our full support to the players involved and want them to know that rugby stands with them in opposing racism. I applaud their courage in raising what must have been a highly distressing experience," he said.
Argentine Rugby Union (UAR) President Gabriel Travaglini also condemned the incident, saying a "group of five or seven individuals" was responsible for the abuse.
Over 20,000 spectators were at the Estadio Bicentenario as England sealed a 2-0 win in the two-match test series.
"Unfortunately, despite an exhaustive search, it was not possible to identify the perpetrators," Travaglini said.
"We will continue to work collaboratively with World Rugby to educate the fans and eradicate any similar manifestations in the future, ensuring that our events are spaces of respect and inclusion for everyone."
England Rugby CEO Bill Sweeney also condemned the abuse.
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"Every player, regardless of their background, has the right to represent their country with pride and dignity, free from discrimination and abuse. We are in close contact with the players affected and have offered them our full support," he said.
"We are pleased that World Rugby was able to act swiftly to investigate and thank UAR for their full cooperation and support throughout. We trust that they will take the necessary steps to prevent any recurrence of such unacceptable behaviour."
In 2020, the UAR stripped Pablo Matera of the captaincy and stood him and two other players down from Argentina's final Tri Nations clash against Australia after the flanker allegedly published discriminatory and xenophobic posts on social media several years earlier.