Investigators are trying to determine what caused the death of a 19-year-old Anaheim woman who attended a concert at the Whittier Narrows Recreation Area on Sunday.
An autopsy was pending for Emily Tran, who was pronounced dead about 5:40 a.m. Monday at a South El Monte hospital, said Ed Winter, a spokesman for the Los Angeles County coroner's office.
Her death was reported as a possible accident, he said.
Investigators are looking into whether drugs were involved and whether she was "given something on purpose or willingly," Winter said.
Tran was taken to the hospital after she went to the health tent about 8:30 p.m. Sunday at the HARD Summer 2014 music festival, KTLA reported.
Preliminary hospital tests suggested Tran tested positive for methamphetamine and other drugs, but toxicology tests to determine the cause of death are pending, said Los Angeles County coroner's Lt. Larry Dietz.
It was the first time HARD held its summer music festival at Whittier Narrows, a park in an unincorporated area of the county that's managed by the Los Angeles County Department of Parks and Recreation.
HARD has been previously held near Chinatown at Los Angeles State Historic Park, which is undergoing construction of a permanent facility.
"We are saddened to learn of her death. Safety is always our No. 1 concern," said county parks spokesman Andre Herndon. "For this event, we worked closely with the concert promoter, law enforcement, emergency medical personnel and security to make sure there is a swift response to any medical emergency."
Herndon said parks officials will meet with all law enforcement and emergency medical personnel who assisted in the event to review what happened.
The two-day musical festival kicked off Saturday, showcasing 75 hip-hop and electronic music performers and carnival rides.