According to the report, the spies are already on the ground in Rio de Janeiro as part of a “highly classified” mission that includes a total of 17 U.S. intelligence agencies that are working in coordination with Brazilian authorities.

“U.S. intelligence agencies are working closely with Brazilian intelligence officials to support their efforts to identify and disrupt potential threats to the Olympic Games in Rio,” Richard Kolko, a spokesman for National Intelligence Director James Clapper, told NBC News.

The U.S. also has hundreds of analysts, law enforcement and special operations on the ground to assist the 85,000 soldiers, police and other security forces Brazil deployed across Rio for the event. Security has been a major concern during these Summer Olympic Games, especially since the Olympic venue is an often chaotic and violent mega-city of 12 million people.

Last month, the FBI said it arrested 11 Brazilians who investigators say were sympathetic to the Islamic State group, a terrorist organization that would be attracted to the possibility of carrying out an attack on the Olympics while the world’s attention is fixed on the games.