The judge leading the investigation into the Beirut port explosion on Friday asked for permission to prosecute high-ranking politicians and security officials and confirmed charges by his predecessor against the outgoing prime minister. Judge Tarek Bitar summoned caretaker prime minister Hassan Diab for questioning and asked parliament to lift immunity granted to three members who are former ministers, the National News Agency reported. Mr Bitar also asked the prime minister's office and the caretaker interior minister for permission to question General Security chief Abbas Ibrahim and State Security chief Maj Gen Tony Saliba. The move comes weeks after people affected by the the blast and the families of victims started questioning the integrity of the investigation and petitioning for an international inquiry into the disaster that claimed more than 200 lives, injured thousands and damaged thousands of properties across the capital. Ten months after the blast, it remains unclear what triggered the explosion of hundreds of tonnes of ammonium nitrate, who owned the explosive chemical or why it was stored for six years at one of the region's busiest ports. After his appointment in February, Mr Bitar vowed to hold those responsible accountable after doubts emerged over the fate of the investigation, which stalled under his predecessor against a backdrop of political bickering. Mr Bitar replaced Judge Fadi Sawan, who was removed by the supreme court after charging Mr Diab, with three other ministers, of criminal negligence in the case. The request to replace Mr Sawan was put forward by former finance ministers Hassan Khalil and Ghazi Zeaiter, both members of Speaker Nabih Berri’s parliamentary bloc. Both officials and Mr Diab snubbed Mr Sawan’s summons, saying he had no authority to question them under the constitution, which protects members of parliament and ministers from prosecution for decisions made in their line of work. On Friday, Mr Bitar summoned Mr Diab for questioning but did not disclose the date of the hearing. He also asked parliament for permission to press charges against Mr Khalil, Mr Zeaiter andformer interior minister Nouhad Mashnouq. The indictment of Mr Diab fuelled tension between President Michel Aoun and prime minister-designate Saad Hariri, who called it an attack on the post of premier, a position reserved for Sunni Muslims under Lebanon's power-sharing system. The presidency, on the other hand, is reserved for a Christian. The political controversy eventually led Judge Sawan to suspend the investigation before he was removed by the supreme court. The stalled investigation prompted calls for an international inquiry by families of victims, who lamented the lack of progress. Their call was backed by a number of legislators from Lebanese Forces, one of the country’s major parties, who petitioned the UN secretary general to demand the formation of an international fact-finding commission.