President Michel Aoun said the blast was caused by 2,750 tonnes of ammonium nitrate stored unsafely in a warehouse.
Many have accused the authorities of corruption, neglect and mismanagement.
The blast killed at least 137 people and injured about 5,000 others, while dozens are still missing. A two-week state of emergency has begun.
“Beirut is crying, Beirut is screaming, people are hysterical and people are tired,” filmmaker Jude Chehab told the BBC, calling for the people responsible to face justice.
Chadia Elmeouchi Noun, a Beirut resident currently in hospital, said: “I’ve known all the time that we are led by incompetent people, incompetent government […] But I tell you something – what they have done now is absolutely criminal.”
On Wednesday, the government announced that a number of Beirut port officials were placed under house arrest pending an investigation into the explosion.
The country’s Supreme Defence Council insisted that those found responsible would face the “maximum punishment”.
Meanwhile, Amnesty International and Human Rights Watch have called for an independent investigation into the blast. In a statement, HRW said it had “serious concerns about the ability of the Lebanese judiciary to conduct a credible and transparent investigation on its own”.
What triggered the explosion?
The ammonium nitrate – which is used as a fertiliser in agriculture and as an explosive – had reportedly been in a warehouse in Beirut port for six years after it was unloaded from a ship impounded in 2013.
The head of Beirut port and the head of the customs authority both told local media that they had written to the judiciary several times asking that the chemical be exported or sold on to ensure port safety.
Port General Manager Hassan Koraytem told OTV they had been aware that the material was dangerous when a court first ordered it stored in the warehouse, “but not to this degree”.
