The death toll rose to four in a food factory boiler explosion case in Karnataka as two others who were hospitalised after the incident, succumbed to injuries on Tuesday.The deceased are identified as Dhanalakshmi (52) and Sachin (40). The condition of another victim Shanthi (40) is also critical, according to police.The incident had taken place at 1.45 p.m. in the premises of MM Food Products factory located on Magadi road. Five people worked in the factory which operated in a single-story building. The deceased Sachin was the partner in business. Dhanalakshmi was a local resident.Sourabh Kumar and Manish Kumar, both from Motihari district Bihar were burnt to death in the explosion. Sachin, Dhanalakshmi and Shanthi suffered severe burn injuries and were shifted to the Victoria hospital.Sourabh Kumar and Manish Kumar had joined work in July. The deceased were in their early twenties and families had fixed their marriages.The impact was such that the asbestos sheet roof of the building was overthrown. Police said they found 15 gas cylinders inside the building.DCP (West) Sanjeev Patil stated that, Joint Director Factories and Boilers Department and a team from Forensic Science Laboratory (FSL) had visited the explosion site and exact cause of the explosion will be ascertained. Magadi Road police are investigating.