Paramedics took 36 fans to the hospital after an Avicii show in Boston, according to the Globe and other local sources.
At least 50 EDM fans at Wednesday's TD Garden show were treated or examined on site. The majority of the illnesses were drug- and alcohol-related, according to authorities.
There were no fatalities, and medical personnel believed all symptoms were relatively minor. Witnesses described a packed scene of teenagers and early-twentysomethings on the dance floor, some of whom told the Globe that it was difficult to breathe or move around.
Avicii also performed last weekend at Electric Daisy Carnival in Las Vegas, where two fans' deaths are still under investigation. At a May Toronto concert, 29 people were hospitalized during Avicii's show.
Michael Bosse, the deputy superintendent for Boston EMS, told the Globe that there may have been club drugs like "molly" in circulation, but authorities have not confirmed that it specifically contributed to any of the illnesses.
The show was the kickoff date of Avicii's new East Coast U.S. and European tour. The artist, born Tim Bergling, has earned two Grammy nominations and scored several pop hits with "Wake Me Up" and "Le7els."
Follow @AugustBrown for breaking music news.