Kolkata: The blast in the underground cable line on the footpath in front of Stephen House at BBD Bag took place due to a short circuit. On Monday, scientists from state Forensic Science Laboratory (FSL) visited the spot and determined the cause.According to FSL experts, apart from CESC and BSNL cables and there were cables of other firms under the footpath. At the particular point where the blast took place, cables of CESC and BSNL criss-crossed. During inspection, FSL team found that some gases leaked from that point. After examining in detail it was found that a portion cable was missing. It is suspected that the particular portion of cable was blown off. Also Read – Bengal family worships Muslim girl as Goddess Durga in Kumari PujaFSL scientists claimed that due to discharge of high energy from the CESC cables, which is commonly known as spark, the cable insulation melted. As a result flammable gases such methane, carbon monoxide and hydrogen were produced from decomposition of insulation cable. Due to flammable gases produced in the chamber high-pressure led to explosion and cables were ignited. But it is assumed that the incident did not take place suddenly. According to the experts, such incidents take a long time to occur. CESC and other organisations are working to fix the cables. Due to the work, traffic movement on Hemanta Basu Sarani was partially obstructed. On Sunday evening, a part of the footpath in front of Stephen House was blown away in a blast. The impact was so severe that the top layer of the pavement was blown away resulting in caving in of the footpath. A police team led by Joint Commissioner of Police (Crime) Murlidhar Sharma rushed to the spot and sniffer dog was also brought to the site. As it was a Sunday chances of loss of life was minimum.