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.
French architect Jean-Marc Bonfils, involved in rebuilding the city after the civil war, and firefighter Sahar Fares, one of the first res-ponders at the scene, were among the first fatalities to be named. A German diplomat was also among the dead.
French President Emmanuel Macron – the first world leader to visit since the tragedy – was mobbed as he walked through the city on Thursday, with residents imploring him to help and denouncing their leaders. “Help us, you are our only hope,” one resident called out. “Please don’t give money to our corrupt government,” said another, before adding: “We can’t take this any more.”
At a press conference, Mr Macron said a new political order was needed in Lebanon. “The anger I saw in Beirut today also showed signs of hope for the future,” he said.
He said France would help organize international aid to Lebanon. Funding was available, he said, but political reforms had to take place before it could be sent. He vowed that there would be no blank cheques for Lebanon’s leaders, but cautioned that he could not tell the Lebanese government what to do. France is the former colonial power in Lebanon.