Joan Rivers -- Clinic Claims NO Biopsy, NO General Anesthesia

The surgery clinic where Joan Rivers' heart stopped beating is calling BS on a report suggesting her death was caused by a biopsy that should have only been performed at a hospital.

Yorkville Endoscopy broke its silence after the New York Daily News story ran ... saying a biopsy was NOT performed during the ill-fated procedure.

The Daily News story claimed a doctor who arrived with Rivers was performing the biopsy after doctors spotted something on her vocal cords, and her vocal cords seized ... leading to a fatal chain of events.

And Yorkville went on to say they do NOT administer general anesthesia, saying they use "light to moderate sedation."

New York authorities are still investigating cause of death.