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.