The 18-year-old woman was transported to San Dimas Community Hospital after collapsing at the music festival. She was pronounced dead at 6:04 p.m.
[Ads /]
The 19-year-old woman was also found unresponsive and transported to Pomona Valley Hospital, where she was pronounced dead at 8:10 p.m.
Their identities were not immediately released pending notification of kin. Autopsies are expected later this week.
About 65,000 people were expected to attend each day of the sold-out two-day music festival, which includes performances by The Weeknd, Jack U, The Chemical Brothers, Dillon Francis, Schoolboy Q and Rae Sremmurd.
HARD Summer was previously held at the Whittier Narrows Recreation Area near South El Monte and at the Los Angeles State Historic Park near Chinatown.
In June, a 24-year-old man died of ecstasy intoxication at the Las Vegas Motor Speedway during the Electric Daisy Carnival.