Judge Fadi Sawan filed the charges against Hassan Diab and former finance minister Ali Hassan Khalil, as well as Ghazi Zeiter and Youssef Fenianos, both former ministers of public works.
All four were charged with negligence leading to deaths over the 4 August explosion at Beirut port, which killed more than 200 people and injured thousands. Some 300,000 people were left homeless.
The explosion was likely caused by 2,750 tonnes of ammonium nitrate that had been poorly stored at the port for years, with the knowledge of politicians, top security officials and even the prime minister and president.
The investigating judge had faced mounting criticism from the public for the secretive investigation and the fact that no senior political figures had been held to account. Before Thursday’s indictment, those detained over the blast were around 30 low-to mid-level security officials and port and customs officials.
Mr Diab, whose cabinet resigned over the August blast after taking office in early 2020, rejected Judge Sawan’s decision saying his conscience was clear and accused the judge of breaching the constitution.
His office has indicated they will not comply, saying in a statement that the judge had violated the constitution by overstepping the role of parliament, which has a special court to indict ministers.
Mr Zeiter said he would comment once he was officially informed. He headed the public works ministry in 2014, soon after the Rhosus cargo ship carrying tonnes of ammonium nitrate arrived at Beirut port.
There was no immediate comment from Mr Fenianos, who followed Mr Zeitar taking up the role as transport and public works minister in 2016 until the beginning of 2020.
Mr Khalil, a top aide to Lebanon’s influential parliament speaker Nabih Berri, said he had no role in the case as former head of the finance ministry, which oversees customs.
He said on Twitter that he was surprised by the judge’s allegations which “violated the constitution and the law”.
The probe has sparked legal debate in Lebanon about whether ministers enjoy immunity in this case.
Families of some of the victims say Judge Sawan told them he had sent Mr Berri a memo calling for immunity to be lifted but the speaker had not accepted his proposal.
The judicial council that appointed Sawan said on Thursday he sent a letter last month telling parliament his investigation had revealed “serious suspicions” linked to some government officials. Parliament replied it found no such suspicions based on the information provided, the council said.
Sawan subsequently decided to interrogate a number of officials “as defendants”, including ministers, and was doing his job to find the culprits, it said.
The news was welcomed by Michel el Murr, head of the search and rescue for the Lebanese fire crew, who lost several colleagues and friends in the blast. He said it was a “positive development” that the prime minister and senior ministers would be questioned as they knew about the dangerous stockpile and had apparently failed to do anything about it.
“We hope this means we will get more answers about what happened and we will be a step closer to justice,” he told The Independent.
Diab, a former university professor, resigned a few days after the blast, which has been described as one of the largest and most devastating non-nuclear explosion in modern history.
Both Khalil and Fenanios were sanctioned by the US in September this year, the first two officials to be subjected to those outside of Hezbollah group.