Investigating Judge Fadi Sawwan has started questioning witnesses as well as former and current ministers as part of a probe into the causes behind the 4 August Beirut blast, the state-run National News Agency (NNA) reported.
Sawwan yesterday questioned four witnesses to the explosion and is set to hear testimonies from other bystanders today.
The lead investigating judge has also reportedly questioned caretaker Prime Minister Hassan Diab over his involvement in the blast and will start probing other former and current ministers in the coming days.
Diab and his cabinet were forced to resign in the aftermath of the explosion after documents came to light claiming that he, President Michel Aoun and former government ministers, were aware the highly explosive substance was stored in the port prior to the blast.
The 4 August blast happened when 2,750 tonnes of ammonium nitrate, stored unsafely in Beirut port's warehouse 12 for six years, ignited and exploded.
The explosion claimed the lives of nearly 200, injured thousands more and caused widespread material damage as far as 15 miles from the site of the blast.
To date, 31 officials have been detained as part of the investigation, many of them employees of the port and customs authority who were put under house arrest, pending questioning, in the days after the blast.
The Director General of Beirut Customs Badri Daher and the Director General of Beirut Port Hassan Qureitem are among those arrested as part of the probe, which is being aided by personnel from the US' FBI.
A French team, who arrived in Beirut ten days after the blast equipped with a helicopter carrier and a crew of forensic police, are also conducting their own investigation into the cause of the explosion.
A host of other countries have sent search and rescue teams to aid the relief effort.
Most recently, a Chilean team working in the eastern Beirut district of Gemmayze spent three days removing rubble hoping to locate a survivor after detecting heat as well as signs of breathing.
The search was called off after the head of the volunteer rescue group Topos Chile, told a press conference his team had combed 95 per cent of the building without locating the potential survivor.
At least seven people remain missing more than a month after the explosion. However, most rescue missions have been called off with relief efforts now focusing on clearing the rubble and finding remains.