Four people were injured, two of them seriously, when a giant video screen collapsed Thursday night during setup for this weekend's Ultra Music Festival in Miami, authorities told NBC News.

The screen collapsed about 7:50 p.m. ET onto the festival's main stage as workers were preparing for the annual electronic music festival, which organizers said is expected to draw more than a quarter-million people to Miami's Bayfront Park over the next two weekends.

A Miami fire official told NBC News that two people suffered serious head injuries and other fractures. NBC 6 of Miami reported that they were being treated at Ryder Trauma Center.

NBCMiami: Stage Collapsed at Site of Ultra Music Festival: Miami Fire-Rescue

The two other victims sustained unspecified minor injuries, the fire official said, with only one of them being taken to the hospital.

The festival, now in its 15th year, is considered one of the leading music events in the world, with a heavy emphasis on electronic music. This year's lineup includes such prominent acts as Hot Chip, Snoop Dogg, Deadmau5, Disclosure and Major Lazer.

Gabe Gutierrez and Justin Kirschner of NBC News contributed to this report.