A Lebanese judge has charged caretaker Prime Minister Hassan Diab and three ex-ministers with criminal neglect over the huge explosion at Beirut's port that killed more than 200 people this summer.

Diab, as well as two former public works ministers and an ex-finance minister, were accused Thursday of criminal neglect "that led to the death and harm of hundreds of people" in the blast on August 4, according to Lebanon's state-owned National News Agency. 

These are the most high-profile indictments in the investigation of an explosion that was believed to have been caused by the detonation of thousands of tons of ammonium nitrate, stored for years at the port of Lebanon's capital. 

Judge Fadi Sawan, who is investigating the incident, is set to question Diab and the ex-ministers next week.

"The Prime Minister's conscience is clear. He is confident that his hands are clean and that he has handled the Beirut Port blast file in a responsible and transparent manner," read a statement from Diab's office on Thursday. "Hassan Diab will not allow the Premiership to be targeted by any party."

Diab's government, which stepped down in the wake of the blast and will be replaced when a new cabinet is formed, has repeatedly acknowledged receiving prior warnings about the dangers posed by the storage of the explosive material at the port. 

Previous governments were also notified about the warehouse, but no one addressed the problem. 

It is unclear what triggered the detonation of the material, but government officials have said that they have not ruled out sabotage. 

The explosion destroyed much of Beirut's eastern coastal area, killing more than 204 people, injuring at least 6,500, and displacing around 300,000 from their homes.

Two of the ex-ministers indicted -- former finance minister Ali Hassan Khalil and former public works minister Youssef Fenianos -- were recently sanctioned by the Trump administration for links to Hezbollah. 

Lebanon's streets, already buckling under the strain of a financial meltdown, political crisis and a global pandemic, have seen widespread anger over the blast. Protesters have been sharply critical of the investigation, which they perceive as slow and lacking in transparency and independence.

By: Tamara Qiblawi and Ghazi Balkiz