MUMBAI: Three labourers were killed and 15 others injured following an explosion and a fire at a chemical plant that spread to four adjoining units in the highly hazardous Tarapur MIDC in Boisar on Thursday night.Around 20 labourers were working in two of the units at night as the plants are usually shut on Fridays owing to weekly power cut in the Maharashtra Industrial Development Corporation (MIDC) area, around 10 km from Tarapur Atomic Power Station .The explosion happened around 11.15pm at Novaphene Specialities Pvt Ltd ’s plant where 25 drums containing 200 litres of solvent each were stocked in the open, Palghar district officials said. The plant manufactures speciality chemicals and cosmetic preservatives dealing in high-purity acid and acid anhydrides, which are organic compounds.The survivors told police that soon there were nearly 40 explosions. Tremors were felt up to around 12km away in Boisar, Mahim and Palghar with residents reporting instances of glass windows and doors shattering.The flames also engulfed Bharat Rasayan, Aarti Drugs, Unimax Chemicals and Prachi Pharmaceuticals, which share a wall with Novaphene. Within 15 minutes, the fire spread to around one acre. The MIDC area has over 1,100 highly flammable units.The electricity board immediately cut power supply to the entire Tarapur-Boisar region. Around 25 fire engines from Boisar, Tarapur, Vasai-Virar, Thane and Bhiwandi rushed to the spot and battled for nearly six hours before bringing the flames under control by 5.15 am. As a few areas continued to burn, search and cooling operations began only around noon. Palghar district superintendent of police Manjunath Singe said rescue personnel found three charred bodies in Aarti Drugs, the third factory to be engulfed in the flames. They were later identified as Pintu Gautam, Janu Agaria, and Aloknath Agaria, all aged 30 and residents of Shiv Nagar in Boisar. Later, resident deputy collector Navnath Jare said no persons are feared trapped in the fire and a close watch is being kept on the affected sites.One of the survivors was shifted to Tunga hospital in Mira Road with serious injuries, while 11 others are undergoing treatment in hospitals in Boisar. Three others were discharged from hospitals after treatment on Friday.The Boisar police have registered a case of accidental death. A case of negligence will be filed after Directorate of Industrial Safety and Health officials who visited the site submit their report. District collector Prashant Narnaware said prima facie it appears that the solvent plant did not follow safety precautions. “If the units are found guilty, a recommendation will be made to the government to cancel their licences,” he said.