The judge investigating an explosion in Beirut that killed hundreds of people has charged Lebanon’s caretaker Prime Minister Hassan Diab and three former ministers with negligence.

In addition to Diab, Judge Fadi Sawwan filed charges against former finance minister Ali Hassan Khalil and former public works ministers Ghazi Zeaiter and Youssef Finianos, Lebanon’s official news agency reported Thursday.

Sawwan charged the four men with carelessness and negligence that resulted in the massive August 4 blast that killed more than 200 people, injured thousands and destroyed large parts of the capital city.

The four are the most high-ranking officials to be indicted to date in the investigation into the explosion, considered among the largest non-nuclear blasts on record.

Humanitarian aid donated by World Food Program (WFP), are unloaded at Beirut's port, in Beirut, Lebanon September 3, 2020…UN to Assist Families Affected by Beirut Blast More than 50,000 people are expected to receive funds for food

Officials have blamed the explosion on the detonation of 2,750 metric tons of ammonium nitrate that had been improperly stored for six years at the Port of Beirut in the heart of the city.

In response to the charges, Diab said his conscience is clear and he is "confident that his hands are clean and that he handled the Beirut port blast file in a responsible and transparent manner.”

Finianos and Khalil did not immediately respond to the charges but Zeaiter told Reuters he would comment after receiving official notice.

Months after the blast, anger continues to mount among victims over the slow pace of the investigation that leaders vowed would produce results within days of the explosion.

Some 30 security, port and customs officials have been detained so far.

Diab resigned in the wake of large anti-government protests a few days after the blast but has continued to serve as caretaker while efforts form a new government continue to be hindered by political disputes.