A toxicology report has surfaced that says two dolphins who died last year after a zoo rave in Switzerland that says heroin was found in the mammals’ urine.

MSN.com reports:

About a year ago, dolphins Shadow and Chelmers died agonizing deaths in Connyland, Switzerland, after the zoo allowed a rave (attended by thousands) to be held near their training pool. For animals with sonar hearing, a possibly dubstep-heavy event was already considered a strain. Now a toxicology report has emerged that shows a heroin substitute was found in the animal’s urine. This would seem to confirm initial suspicions that whacked-out ravers fed the dolphins drugs while possibly on some kind of weird acid trip.

AOL UK reports that it was originally believed that the techno music pumping out from the club just yards from the dolphins’ pool had caused their deaths: