An undetected drug allegedly passed around at a music festival in Tampa, Florida killed two young people and sickened 57 others, with one attendee describing the concert as “really uncontrolled.” Meanwhile, police are looking into the causes of death.

So far, Florida residents Katie Bermudez of Kissimmee, and Alex Haynes of Melbourne are the only two confirmed deaths. Both were rushed from the Sunset Music Festival in Tampa to a hospital over the weekend.

Haynes, 22, was hospitalized on Saturday, the first day of the festival, and was pronounced dead on Sunday. Bermudez, 21, died on Monday, the day after she was hospitalized, Tampa Police spokesman Steve Hegarty said.

“The social worker said, ‘Your daughter Katie is on a ventilator. You need to get to the hospital,'” Nancy Bermudez told Fox affiliate WTVT, recalling a 3am phone call from St. Joseph’s Hospital.

Bermudez’s symptoms included high fever and brain swelling, but doctors couldn’t find a way to save her.

“We don’t know [what happened]… They have an autopsy going on,” her mother Nancy said. “The hospital didn’t know; they were bewildered with how to treat this.”

A Hillsborough County Medical Examiner concluded that the young people likely died from a drug overdose. Police have not provided any information on what substance might have killed Katie and Alex, but tentatively linked their deaths to the Sunset Music Festival, an electronic dance music concert that was attended by more than 30,000 people this year.

A Tampa Fire Rescue spokesperson said that crews took a total of 57 festival-goers to the hospital over the course of the two-day event.

“Obviously, that type of music tends to attract a certain type of fan that engages in certain types of drugs,” Mayor Bob Buckhorn said on Tuesday, according to the Tampa Bay Times. “It worries me any time we have a loss of life here, particularly when it could have been prevented by better decision-making.”

The festival organizers have refused to comment on the deaths, citing an “ongoing investigation,” while stressing concerns over the “safety and welfare of our fans.”

“The health, safety and welfare of our fans and community is Sunset Music Festival’s first priority and we take every measure to create a safe environment at our events,” the organizers told NBC-affiliate WFLA in an emailed statement. “Any loss of life is a tragedy and we extend our deepest heartfelt condolences to the family and friends of those affected. Due to the ongoing investigation by the medical examiner’s office, Sunset will not issue additional comments at this time.”

However, one of the festival’s regular visitors told the Tampa Bay Times that this year’s Sunset concert “was really uncontrolled.”

“No one really knows what they’re taking,” said Valerie Rodriguez of Tampa, stressing that this was the first time she had seen so many people being rushed to a hospital.

Rodriguez, 20, said the situation made her “nervous.”

Tampa police said they had made 33 arrests, handed out 16 marijuana citations, and issued four noise complaints at the concert.