Clowns gathered at a convention in Mexico City have denied any of their colleagues were behind the killing of a former drug cartel leader last Friday.
Francisco Rafael Arellano Felix, 63, was killed in a beach resort in Baja California in north-western Mexico.
Gunmen dressed as clowns opened fire on the former leading member of the once-powerful and violent Tijuana cartel, authorities say.
Around 500 clowns at the convention held a "laugh-a-ton" rally for peace.
A clown leader said if a real member of the profession had been involved in the shooting, they would have been easily identifiable by their costumes, masks and painting.
"The people who do that, they're not clowns. I can swear on my mother's grave it wasn't a clown," Tomas Morales, whose stage name is Clown Llantom, told Associated Press news agency.
They say clowns are frequently victims of robberies and their costumes and masks are then used to commit other crimes.
The attack against Francisco Rafael Arellano Felix took place during a family party at a rented beach house in the tourist resort of Cabo San Lucas.
Security experts believe the Tijuana cartel is now run by his sister Enedina and her son Fernando, known as "The Engineer", according to AFP news agency.
Most estimates put the number of people killed in Mexican drug-related violence since late 2006 at more than 60,000.