Video has emerged of the moment fireworks struck a crowd at a music festival in the Czech Republic, with promoters blaming human error.
The incident took place at Transmission, a huge trance music event held at Prague's O2 Arena over the weekend.
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No serious injuries have been reported, but the event's management has apologised for "exposing" revellers to "the situation".
"A human mistake was made with installing a substitute effect for the original product that wasn't available. This should have been avoided," Transmission says in an official statement.
"Even though the pyro show was all the time under full control of licensed pyrotechnicians nevertheless, not everything has gone according to plan [sic].
"On behalf of everyone involved we apologize for the situation, you have been exposed to."
The statement adds that as a precaution, there won't be overhead pyrotechnic displays at future festivals.
Transmission had a maximum capacity of 16,800 visitors and features artists including Markus Schulz, Aly & Fila, Ferry Corsten and Driftmoon.