HOUSTON — Three people were taken to the hospital Saturday for minor knee injuries after getting trampled at the Astroworld Festival, according to the Houston Fire Department.

A few minutes before the gates were scheduled to open, attendees climbed over gates and stampeded toward the entrance.

The mayhem was captured on video.

Houston police said they are sending extra officers to NRG to control the crowd. They admitted they were initially understaffed for the event. 

Police said some people were trying to cut through gates using bolt cutters. 

Gates to the festival opened at noon. 

RELATED: Here's everything you need to know if you're headed to the Astroworld Festival

More than 50,000 people were expected to attend this year’s event, which sold out long before the lineup was released. The festival has become the largest single-day artist-curated music festival in the country.

Travis Scott released the lineup Friday. Here are the artists expected to perform:

  • Travis Scott
  • Gucci Mane
  • Migos
  • Tay Keith
  • Pop Smoke
  • Rosalia
  • Young Thug
  • Young Dolph + Key Glock
  • Pharrell
  • Sheck Wes
  • DaBaby
  • Marilyn Manson
  • Megan Thee Stallion
  • Playboi Carti
  • Don Toliver

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