Police said the pair were detained after two pro-Palestinian groups alleged they had been waving flags from their army brigade.

Video showed thick plumes of black smoke rising from the famed festival grounds in Boom, Belgium on Wednesday. Fireworks could also be seen and heard going off in the distance.

A festival spokesperson said in an emailed statement that a 35-year-old Canadian woman fell ill at the event Friday and was hospitalized. But organizers were told Saturday morning she had died.