Private companies operating at Beirut port’s free zone say a massive fire that destroyed several warehouses on Thursday was a result from lax oversight of repairs following the deadly blast that tore through the city month ago. The fire started in the early afternoon, sending clouds of black smoke above the city and terrifying residents still reeling from the explosion of 2,750 tonnes of ammonium nitrate at the port on August 4 that killed nearly 200 and injured 6,500. Firefighters, civil defence volunteers and an army helicopter struggled until 8pm to bring the blaze under control as it spread rapidly between warehouses storing flammable products such as cooking oil and tyres, the head of the fire department rescue team, Lt Michel El Murr said. The fire was still smouldering 24 hours later. The state-run National News Agency reported on Friday morning that the military police was in the process of interrogating "roughly 20 people". These include maintenance workers and an administrator at Beirut Cargo Centre (BCC), the company that owns the warehouse where the fire started. State prosecutor Ghassan Oueidate tasked all major security agencies to investigate the causes of the incident. Public Works Minister Michel Najjar said on Thursday evening that the fire was caused by “someone carrying out repairs using an angle grinder which led to sparks and a fire”. Joseph Khoury, an employee at one of the dozens of private companies operating at the port's free zone, said that security measures had not been enforced as strictly as they were before last month's blast. “In normal times, safety measures are thorough in the free zone. But after the August 4 explosion, we all worked at the same time to fix our warehouses. These are exceptional times, and the state is overstretched and not present to supervise the work," said Mr Khoury, who works for the Lebanese franchise of ECU Worldwide, an international cargo company. Maintenance work in the free zone area must first be cleared by the army intelligence, he said. Additionally, customs, port security services and the head of the logistics zone must all be informed of operations in the duty free area. “We needed to wait several weeks to obtain the permission to put just a small antenna on top of our warehouse,” he said. “A representative of the state – whether it be the army, customs or port security – normally supervises maintenance work.” The head of the Beirut port, Bassem Al Qaisi, was not immediately available for comment. Local media reported that he would issue a circular on Friday banning storage of dangerous materials at the port, more than a month after the deadly explosion. Mr Khoury's colleague and brother, Alain, witnessed the start of the fire on Thursday as he was cleaning up the ECU warehouse. "They were welding metal bars to fix the warehouse and in a fraction of a second, a big fire started that spread really fast," he told <em>The National</em>. The explosion that devastated large parts of Beirut had a similar trigger. Lebanese authorities said welders accidentally set off a fire at a hangar storing fireworks and ammonium nitrate, causing both to explode. Already berated for their negligence and corruption, the Lebanese authorities were harshly criticised again on Thursday for failing to secure the port properly. “I just cannot fathom how a fire of this scale is possible in the port. Did authorities not ensure all material was safely stored after negligence destroyed half the city?” tweeted Human Rights Watch Lebanon researcher Aya Majzoub. Magdi Ghossainy, deputy general manager at logistics company Radec, said that he believed that its warehouses at the free zone were “totally damaged”. "I think that the two warehouses most affected were BCC's and ours because in our warehouse we had stored tyres for re-export," he told <em>The National</em>. "It was very hard for the firemen to control the fire because of these tyres." Asked about security measures at the free zone, Mr Ghossainy said that “there is a procedure for companies to follow. I don’t know if they all do their work or not but there should be more measures”. “Let’s say we wanted to hire engineers to rebuild and assess damages after the explosion, we would have had to submit a list of names with phone numbers and addresses of what they do and get the authorisation from the military police,” he said. However, Radec has not started this process yet so Mr Ghossainy was unsure whether a state representative should be present to supervise maintenance works. One of the warehouses damaged on Thursday stored food for the International Committee of the Red Cross. Fabrizio Carboni, Red Cross director for the Near and Middle East, said 500,000 litres of cooking oil and food parcels were stored at the site. “Our humanitarian operation risks to be seriously disrupted,” Mr Carboni wrote on Twitter. Compounding the lack of safety measures, Beirut’s firefighters have been under-equipped since the port explosion, which killed 10 of its members who had rushed to extinguish the initial fire, unaware of the dangerous chemicals stored nearby. The blast destroyed 29 of the 31 firefighting and emergency response vehicles parked at the fire department's headquarters in the Qarantina neighborhood near the port, said Lt El Murr. About 10 vehicles were mobilised on Thursday after calling for assistance from fire stations in other Beirut neighborhoods, he said. Italy donated 10 new firefighting trucks after the port explosion, but they are not operational yet because of technical differences and because they still have not been registered with local authorities. “We are waiting for the papers so that we can start using them,” said Lt El Murr.