Three dozen teenagers at an electronic dance concert at Boston's TD Garden were taken to local hospitals on Wednesday, the Boston Herald reported, citing a city official.
Many attendees arrived already intoxicated to the event, the newspaper said, quoting Deputy Emergency Medical Services Superintendent Mike Bosse.
McKenzie Ridings, a spokeswoman for the department, told Reuters said she could confirm that three attendees were transported to local hospitals, but could not give their conditions.
The Boston Globe reported that as many as 38 attendees were taken to the hospital after ingesting a "dangerous" substance, but that all of their symptoms were minor.
The show included a performance by the Swedish DJ Avicii, both newspapers said.
(This story was refiled to add dropped letter in fifth paragraph)
(Reporting by Sharon Bernstein; Editing by Michael Perry)