Beirut, Sep 4 : Outgoing Lebanese Prime Minister Hassan Diab became the country's highest ranking official to be questioned over the August 4 Port of Beirut blasts that claimed the lives of 191 people and caused widespread destruction in the capital city. Diab was questioned by judicial investigator Fadi Sawan on Thursday, reports Xinhua news agency. Sources has previously said that the Lebanese judicial system will also question current and former public works ministers over the explosions. The system has so far arrested several employees at Beirut's port and investigations are still ongoing into the biggest disaster witnessed in Lebanon since the assassination of late Prime Minister Rafic Hariri in 2005. Reports revealed that a number of Lebanese officials were aware about the existence of chemicals at the port. Besides the victims, the blasts also injured about 6,500 people. It also destroyed a big part of the city and the damage was estimated to be over $15 billion. On Thursday, the new director of Beirut's port revealed the existence of around 4.35 tonnes of ammonium nNitrate near the entrance of the port, urging authorities to re-export the materials to prevent another disaster. On August 11, Diab, who was appointed Prime Minister in January after months of deadlock, announced his cabinet's resignation after many people accused the country's leaders of culpability through their alleged negligence and corruption. On Monday, Mustapha Adib, the country's former Ambassador to Germany, was named the new Prime Minister. /IANS