New York ( CNN ) -- The third and final day of New York City 's Electric Zoo music festival was canceled Sunday after two concert-goers died and at least four others were hospitalized due to drug-related causes , police said . The cause of death for the two Electric Zoo attendees is believed to involve the drug MDMA , either in Ecstasy pills or in its `` pure '' powder or crystal form , known as molly . Police identified the two victims as Jeffrey Russ , 23 , and Olivia Rotondo , 20 . Four others remain hospitalized and critically ill , with the causes still under investigation , according to Sgt . Lee Jones , a New York Police Department spokesman . The city recommended the electronic music festival be canceled after the recent events , and Electric Zoo 's promoters , Made Event , agreed , Jones said . In a statement posted Sunday on the event 's homepage , Made Event said `` the founders of Electric Zoo send our deepest condolences to the families of the two people who passed away this weekend . Because there is nothing more important to us than our patrons , we have decided in consultation with the New York City Parks Department that there will be no show today . '' Social media postings regarding Electric Zoo 's cancellation vary from sympathetic to downright infuriated . General admission passes cost $ 179 per day for the festival , held at Randall 's Island Park in the East River . The promoters ' website said people who bought tickets for Sunday would get full refunds . `` Large bags , '' `` bad attitudes '' and `` illegal substances '' were among the 22 listed types of items prohibited at the venue , and everyone was searched upon entry , according to the website . Founded in 2009 , Electric Zoo features electronic dance music , with more than 110,000 people attending the festival in 2012 . The three-day festival started on Friday and was scheduled to run through Sunday night . What is MDMA ? MDMA was created in Germany in the early 1900s , according to the National Institute on Drug Abuse . Decades later , the drug found fans across the Atlantic . During the 1970s some American psychiatrists felt they 'd found in the drug a kind of `` penicillin for the soul . '' The drug was said to allow for greater insights and better communication . U.S. officials disagreed , and in the 1985 the Drug Enforcement Administration banned the substance as a Schedule I drug , meaning it had no proven therapeutic value . In the 1990s , MDMA gained a reputation for party drug at all-night warehouse parties known as raves . Emergency-room visits rose steadily from 421 in 1995 to a peak of 5,542 in 2001 , according to DEA statistics . Questions were raised about safety and purity of Ecstasy . That 's when molly was born . Molly -- short for `` molecule '' -- is touted as the pure form of MDMA , but a spokesman for the DEA says do n't believe the hype . According to Rusty Payne , the agency sees MDMA from Asia , Canada and the Netherlands . `` You have no idea the lab environment these chemicals or substances were produced in , '' Payne said . `` If they knew where things were produced , they might think twice . '' In 2009 , government data found 22,816 emergency-room visits due to MDMA , a 123 % percent increase from 2005 . But molly has fans among some in the medical field . An article published last year in the Journal of Psychopharmacology found that the drug helped reduce the symptoms of PTSD for two-thirds of those enrolled in a study . Still , the sample size in that study was small , just 19 people . More studies are in the works . Despite any potential for future uses , authorities warn that the drug is dangerous . After a giant New Year 's Eve party in Los Angeles in 2010 , one person died and 18 others were hospitalized for issues relating to MDMA use , according to the Centers for Disease Control and Prevention . CNN 's Chris Kokenes and Emma Lacey-Bordeaux contributed to this report .
LA : Police identify the two men . NEW : Promoters offer money to people who buy free tickets . Deaths of two Electric Zoo concert - attendees believed to be related to MDMA , police say . Electric Zoo promoters agreed to city 's recommendation that the festival be canceled .