Two of Paris’ biggest and most famous tourist attractions were cleared and closed on Saturday in response to attack threats.

Around 15,000 visitors were requested to leave the Louvre in central Paris after the museum “received a written message stating that there was a risk to the museum and its visitors,” a museum spokeswoman told French news agency AFP.

She didn’t initially elaborate on the precise nature of the threat but French broadcaster BFMTV cited police sources who said the museum had received “bomb threats.”

Alarms rang out through the museum and in the underground shopping center beneath its signature pyramid, with some visitors hurrying to the exits and others reportedly taking photographs.

Later in the afternoon, the Palace of Versailles on the outskirts of Paris was also evacuated after security services received an anonymous bomb threat.