Festival founder Claude Nobs was due to announce the lineup for one of Europe’s most prestigious music events on Thursday, coinciding with tickets going on sale. But the program appeared on the Internet, and soon afterwards in Swiss media, on Tuesday, leading organizers to post the entire lineup except for two events.

“There were leaks, but I can’t confirm we were hacked,” spokesman Pascal Buchs told Reuters. Carlos Santana and John McLaughlin open on Friday, July 1 in the Stravinski Auditorium and return to the stage two nights later along with Susan Tedeschi and others in a tribute to blues king B.B. King, who plays his own gig on July 2.