Rescuers combed through the rubble of Beirut port Friday in a search for survivors watched breathlessly by relatives of the missing, after an investigation into the huge blast made its first arrests.

Shock has turned to anger in Lebanon since Tuesday’s colossal explosion killed at least 154 people and devastated swathes of the capital, with security forces firing tear gas at demonstrators who gathered near parliament late Thursday.

The revelation that a huge shipment of hazardous ammonium nitrate fertiliser had languished for years in a warehouse in the heart of the capital served as shocking proof to many Lebanese of the rot at the core of their political system.