At least five persons were killed in a massive explosion in a boiler that ripped through the Manas Agro Industries & Sugar Ltd. plant at Bela here on Saturday afternoon, the police said.According to an official of Nagpur Rural Police, at around 2.14 p.m., the blast rocked the factory followed by a fire, grievously burning and killing the workers instantly.The sugar factory is part of the Manas Group, and was earlier known as Purti Power & Sugar Factory, owned by Union Minister Nitin Gadkari's family."Prima facie, it appears that the victims were doing some welding work at this particular site and some gas leak may have led to the explosion. The real causes will come out after the probe by the concerned department. We are investigating the matter and lodging the necessary complaints," Superintendent of Police Rakesh Ola, who rushed to the site, told IANS.The victims have been identified as Liladhar W. Shende, 42, Vasudev Ladi, 30, Praful P. Moon, 25, Sachin P. Waghmare, 24 and Mangesh P. Nakerkar, 21. The police had to pacify the angry crowd before the bodies could be removed from the spot.Waghmare was the welder at the plant and the others were his team of helpers, and all were engaged in some maintenance work at the time of the explosion which was followed by a fire and clouds of smoke billowing from the premises.Expressing shock over the tragedy, Shiv Sena leader Kishore Tiwari called for a thorough time-bound probe into the incident to determine whether norms governing the boiler management were adhered to, and follow up with stringent action against the factory officials found negligent."All the labourers killed are Dalits and it is the obligation of the factory management to pay a compensation of Rs 1 crore to the families of each of the victims as they have lost their breadwinners," Tiwari said.According to some videos of the post-blast scene, at least one two-wheeler vehicle was damaged in the blast.