The big stage at the festival is always ornate and extravagant, now only the iron scaffolding is visible naked under the flames.

The festival in the city of Boom in Belgium is scheduled to start on Friday, July 18, so there are no visitors at the festival site.

However, around a thousand people work at the site and have had to evacuate. According to VRT, it is unclear if anyone is injured.

Fireworks can be heard exploding in the blaze.

– Those fireworks are for the DJ acts at Tomorrowland. It is not yet clear if that is the cause of the fire, says Helen Goedgebeur, a reporter at VRT in their live broadcast from the scene.

The fire is not under control but the smoke plume has decreased in size, according to Goedgebeur.

Almost half a million visitors

The electronic dance music festival, which takes place over two weekends in July, is one of the world's largest, attracting around 400,000 visitors last year.

During the first weekend, which is scheduled for July 18-20, Martin Garrix, Axwell and Alan Walker, among others, are booked.

Tomorrowland has not yet announced whether the festival will take place as planned.

– This is of course a huge disaster for the festival and will have major consequences. There was even a sound check here for some DJs today, and tomorrow the first festival visitors were expected. It remains to be seen whether the festival can continue as planned, Goedgebeur tells VRT.