Pictures posted on social media showed festival goers running away from a stage engulfed by flames, Xinhua news agency quoted Sky News as saying.
The Director General of Civil Protection in Catalunya posted on Twitter that no injuries had yet been reported.
Pyrotechnics on the stage have been blamed, British newspaper Daily Mirror quoted Spanish media as reporting.
A video shared on social media shows how the blaze erupted in a matter of seconds as the speaker system was engulfed in fire, triggering music fans to run for safety.
The emergency evacuation procedure flashed on the stage screen as the flames erupted, according to Daily Mirror.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
About VDC
Doraiah Chowdary Vundavally is a Software engineer at VTech . He is the news editor of SocialNews.XYZ and Freelance writer-contributes Telugu and English Columns on Films, Politics, and Gossips. He is the primary contributor for South Cinema Section of SocialNews.XYZ. His mission is to help to develop SocialNews.XYZ into a News website that has no bias or judgement towards any.