The European Organisation for Nuclear Research (Cern) has launched an investigation after a video depicting a mock human sacrifice was filmed on its Geneva campus, a spokeswoman said.
The video, which has been circulating online for days, shows black hooded figure gathered in a main square at Europe's top physics lab, under a statue of the Hindu goddess Shiva. In what appears to be an occult ceremony, the sacrifice of a female victim is staged.
The video was picked up by online conspiracy forums, which have long claimed that occult practices take place at Cern.
A spokeswoman for Cern said the mock ceremony had taken place on its premises without permission.
"These scenes were filmed on our premises but without official permission or knowledge," a Cern spokeswoman told Agence France-Presse in an email.
"Cern does not condone this type of spoof, which can give rise to misunderstandings about the scientific nature of our work."
The investigation under way was an "internal matter", she added.
"Cern welcomes every year thousands of scientific users from all over the world and sometimes some of them let their humour go too far. This is what happened on this occasion," she continued.
The institute hosts sophisticated machinery, including the Hadron Collider, used by scientists to carry out advanced research into particle physics.