More than 25,000 people attended the sold-out, two-day Paradiso Festival, which featured dozens of electronic music performances Friday and Saturday.
Patrick D. Witkowski, 21, of the Seattle suburb of Des Moines, died Sunday at Central Washington Hospital in Wenatchee. He was identified late Monday by Chelan County Coroner Wayne Harris.
An autopsy found no physical injuries or pre-existing medical conditions that would have caused the death, Harris said.
Toxicology tests of blood and urine, with results expected in about eight weeks, should pinpoint a cause of death, he said.
Witkowski was one of seven people from the music festival who were taken to the hospital. Three remained in serious condition, said Kathy Hamilton, director of community relations.
Quincy Valley Medical Center, the closest hospital to the amphitheater, treated about 70 other concert-goers in its emergency room from Thursday through Sunday, spokeswoman Michele Wurl said, with at least 40 of the cases related to drugs and alcohol.
The small, rural hospital has no intensive care unit and serious cases were transferred.
"We deal with the Gorge all summer long," Wurl said. "What we're seeing this year is much higher acuity - more severe - in the drug use.
"They don't even know what they're taking," Wurl said. "They take a hit and 30 to 45 minutes later they take a second. So they get them maxing out one after another. ... We're not talking about too much drinking or smoking a little marijuana."
Some concertgoers were referring to a substance they called Molly.
Deputies handled 62 calls for service at the Paradiso Festival and arrested 23 people for various charges, including possession or delivery of controlled substances, trespassing, obstructing a public servant, assault and disorderly conduct, the Grant County sheriff's office said in a statement. The concert promoter contracts with the sheriff's office to supplement security.
The number of arrests is not unusual for a concert at the Gorge, said Undersheriff Dave Ponozzo. Some people seen by medical personnel were using Molly or MDMA, he said. MDMA is also known as ecstasy.
The sheriff's office said a 20-year-old Seattle man had been found disoriented but OK on Monday after wandering lost for hours. Sgt. Mike Crowder said the young man said he took Molly on Sunday and had a bad reaction.
"Most in attendance were very respectful people to us and to one another," Ponozzo said in an email. "I found them to be very social people, many of who went out of their way to thank us for being there."
Most of the audience stays at a campground on the site overlooking the Columbia River about 120 miles east of Seattle.
Concerts at the Gorge put pressure on the Quincy Valley Medical Center emergency room, which typically sees about nine people a day. The Paradiso Festival was the third concert this year at the Gorge.
In a statement emailed Monday, festival co-producers Live Nation and USC Events said they were "committed to bringing people together to experience music in a safe environment."
"We wish to express our deep concern about reports regarding a 21-year-old man who died at Central Washington Hospital over the weekend," the statement added. "We extend our sympathy to his family."