The deaths of 20-year old Olivia Rotondo and 23-year old Jeffrey Russ at the Electric Zoo music festival last month were in fact caused by an overdose of the drug MDMA, the city's medical examiner's office confirmed, though methylone—a substance that mimics the effects of MDMA but is often toxic—was also found in Russ's system. The office also confirmed that 20-year-old Matthew Rybarczyk died from methylone in June.

According to the medical examiner, Rotondo's death was due to "acute methylenedioxymethamphetamine (MDMA) intoxication with hyperthermia," while Russ's death was caused by "acute intoxication by the combined effects of methylenedioxymethamphetimine (MDMA) and methylone with hyperthermia.

In an unrelated incident, Rybarczyk perished following a party on Governors Island after ingesting what he believed was molly, but turned out to be methylone, a derivative of bath salts.

Though bath salts are illegal in New York State, methylone is not covered under the ban despite being federally classified as a Schedule 1 drug.

"We urgently need a law that would allow us to prosecute the sale of this deadly substance," Special Narcotics Prosecutor Bridget Brennan said recently. Such a law was in fact passed in the last legislative session, and is expected to be signed by Governor Cuomo soon.