One of the first things your friends will tell you when you take ecstasy for the first time is to drink water so you avoid overheating. What they won’t tell you, and likely don’t even know themselves, is that it’s possible to drink too much water leading to water poisoning, which can be fatal.

Such was the case for two women traveling to Tomorrowland this summer who both passed away during the festival, one each weekend. The two victims were a 33-year-old Czech woman and a 26-year old Indian woman.

Judicial Authorities said in a released statement, “By taking [ecstasy] a hormone was created in the women’s bodies that caused them to retain a lot of water in their bodies. The combination of the drugs, sweating, the warm temperatures and possibly dancing meant that the two women drunk too much water. It was this so-called water intoxication that led to their deaths.”

The preliminary investigation believed that their deaths were the direct result of an overdose, but the actual findings paint a more bleak picture.

The Antwerp Judicial authorities told media, “We are now going to get around the table with all the various parties in order to optimize the exchange of information concerning such complex cases with the ultimate goal of carrying out a more thorough investigation into those that are supplying drugs.”