Police said nearly 800 people were treated for medical conditions, but only 25 were taken to hospitals for treatment from to the three-night electronic music festival that organizers said drew about 400,000 people during its three-night run at the Las Vegas Motor Speedway.
Medical examiners will need the results of blood toxicology tests before they can say how 25-year-old Anthony Anaya and 24-year-old Montgomery Tsang died, Clark County Coroner Michael Murphy said.
Anaya, from Everett, was reported dead late Saturday at the Vdara resort on the Las Vegas Strip after attending the festival.
Tsang, from San Leandro, California, died Saturday morning after being taken by ambulance from the festival to the hospital.
Event producer Insomniac issued a statement saying it was "deeply saddened" by the death and hoped attendees would keep the gathering safe.
Police said both deaths were believed to have involved medical conditions.
Festival organizers told police that 134,000 fans attended shows Friday, Saturday and Sunday nights featuring pulsing lights, Ferris wheels, seven stages of music and DJs including Avicii, Diplo, Afrojack and Tiesto.
Las Vegas police said 794 festival-goers received medical attention during the weekend, and officers made 73 felony drug arrests and 21 misdemeanor arrests for less serious charges.
The event moved to Las Vegas four years ago from the Los Angeles Memorial Coliseum after 2010, when a 15-year-old girl died after being treated for drug intoxication, and 114 people were arrested on misconduct, drug and other charges.
Tourism officials in Las Vegas welcome the hundreds of millions of dollars the festival pumps into the Las Vegas-area economy. But several deaths have been reported over the years.
In 2012, a 31-year-old Florida man died after being hit by a truck while leaving the Speedway, and a 22-year-old University of Arizona pre-med student fell from the 27th floor of her hotel room. The woman was found to have Ecstasy and traces of methamphetamine and gamma-hydroxybutyric in her system, but her death was ruled an accident.