Local media from the city of Vigo reported 266 injured, five seriously, after a wooden platform they were standing on gave way beneath their feet. People could be seen falling into the sea, a horrific sight to witness during what was supposed to be an evening of entertainment.

The festival in question is O Marisquiño; a music, urban culture and extreme sports festival held annually in the city of Vigo in northern Spain.

The incident happened just before midnight on Sunday during the set of Majorcan rapper Rels B, who took to Twitter immediately after to wish 'strength' for all those injured.

The cause of the collapse isn't yet clear, whether the structure was weak or there were too many people on it remains to be seen. The Mayor of Vigo has called for a full investigation to determine the cause.

Accidente horrible en #Vigo durante un concierto del @omarisquino. Estamos pendientes de que las ambulancias se lleven a los heridos más leves. Esto pudo ser una tragedia. Escalofriante cómo ha quedado la zona. pic.twitter.com/hAdOwDC2CO

— Miguel Fidalgo (@Miguel_Fidalgo) August 13, 2018

Translated: "Horrible crash in #Vigo during a performance at the @omarisquino [festival]. We are waiting for the ambulances to take the more seriously wounded. This could become a tragedy. The area has become chilling."

Following the collapse, festival-goers were left treading the water with police and civilians alike rushing to help. Watch a video of the aftermath below:

Accidente en #OMarisquiño

Toda la información sobre el suceso que empaña la despedida del festival la tenéis aquí https://t.co/UPri79EdjM pic.twitter.com/t3w2neiDLg

— Faro de Vigo (@Farodevigo) August 12, 2018

The festival have released a comment on their Facebook page