15 January 1978,
The Scala room in Barcelona was burnt down and four workers died. That day a demonstration was held by the CNT Union against the Moncloa Treaties. The Spanish police arrested a number of anarchists by accusing them of the fire, although it was later proved that the person responsible for the attack was a police confidant to start the assembly against them.
Source:
Jonathan Martinez (Audience, January 14, 2018).