There was lots of smoke initially, which made think it was gunpowder, not at all a military style explosive. Also one picture showed a large orange fireball, again a sign of a pyrogenic explosive, like gunpowder. If an 81mm antipersonnel mortar round had gone off in that crowded there would have been scores of people killed. Any a cellphone or pocket camera would only have captured a complete blurr.
I’m not a pyrotechnian, and will gladly defer to anyone with better knowledge, but that was my immediate impression.