Four people were injured—two of them critically—when a section of a suspended LED screen fell from a stage as it was being set up for the Ultra Music Festival in Miami yesterday. CBS Miami reports that the Miami Fire Department has described two of the workers’ injuries as “life threatening.”

The accident took place as elements of the main stage were being built for the festival, which kicks off the first of its two weekends tonight. Further work on the stage was immediately suspended pending an assessment of the structure by engineers, who will be investigating the stability of Ultra’s other stages as well. Festival organizers released the following statement last night:

Today as preparations were being made for this weekend’s Ultra Music Festival, a section of an LED screen fell and injured two workers. Fire Rescue was on site so there was a rapid response. Festival organizers are working with, and supporting, authorities as they investigate the details behind the accident.

The festival will still carry on, though not exactly as planned. The Miami Herald reports that, as a result of the accident, a large section of the festival will be closed off to concertgoers this weekend.

Skrillex, David Guetta, Deadmau5, Calvin Harris, Snoop Lion, Swedish House Mafia and many more will be at this year’s Ultra Music Festival. The event will take place over two weekends for the first time this year.