AHMEDABAD, Aug 19: In a freak industrial accident three labourers were killed and four others fell sick after they cleaned a chemical garbage of a factory in Naroda industrial area on Tuesday.Police said the labourers, about seven in number, working near the Nana Chiloda railway crossing, were hired on August 12 by Pravin Gordhanbhai Patel, proprietor of Gayatri Industries. They were told to clean and dispose of the chemical garbage inside the factory.On the first day, the labourers cleaned the premises, but two of them - Mohabbat Singh Chhanaji Thakore (18) and Kantiji Dhulaji Thakore complained of irritation and blood in the urine. All the labourers had visited their house the same day, police said.But things aggravated when Mohabbat and Kantiji were admitted to a private hospital in Dahegam on August 13 by their family members. The remaining five labourers finished the cleaning and collected Rs 1,200 from Gayatri Industries, the next day. Police said that after two days, Mohabbat found that the skin of his hands and legs was turning dark. He informed the doctors but to no avail. He was later, rushed to Civil Hospital on Sunday where he died at around 11 p.m. Kanti also breathed his last in the hospital during the wee hours of Monday.In the meantime, another labourer Ashok Udaji Thakore was admitted to Civil Hospital where he was pronounced dead at about 3.30 a.m. on Tuesday. The suspicious demise of the three labourers created panic in the area and the family members of the deceased informed the police.Four other labourers Vinu Jitubhai Dantani, Pasha Kuberbhai Parmar, Samal Jethabhai Pandya and Chatur Somabhai Dodia were admitted in C-5 ward of Civil Hospital for treatment, police said.The Naroda police have registered a case against factory owners Pravin Patel and Bhupendra Chunilal Patel. Police said that all the labourers hailed from Vadodara village of Gandhinagar district and used to work as daily wage labourers in different factories.Meanwhile, municipal commissioner B K Sinha said the corporation under Article 37 (1) of the Bombay Provincial Municipal Corporations Act (BPMC) had forced closure of the factory from Tuesday.Sinha said the Gayatri Chemical Industry was manufacturing Meta Phenyl Dieamine. The corporation after the incident took samples of the products and also of the other chemicals from the factory. The samples have been sent for further analysis.