The actors are friends of RICK RIZZOLO, owner of Las Vegas, Nevada, stripclub Crazy Horse, which is currently at the centre of an FBI investigation.
Rizzolo's lawyer TONY SGRO tells the New York Daily News, "(The FBI) has interviewed some of Mr. Rizzolo's celebrity friends.
"(They) have tried to make those friends nervous in order to cause those friendships to end. To suggest that any of those friends know anything with regard to the Crazy Horse is absurd."
Clooney met Rizzolo while filming OCEAN'S ELEVEN in Crazy Horse, while De Niro visited the club when he was starring in CASINO.
According to reports, Rizzolo has been under investigation for ten years for alleged tax evasion and links to organised crime.