FIVE persons, including three brothers, were asphyxiated to death after poisonous gas emanated from a chemical tank which they were cleaning at a leather factory at Vaniyambadi on Friday. Vaniyambadi DSP Gurusamy said that on Friday morning, a group of five contract labourers were cleaning the chemical tanks in a leather factory on Kutcheri Road at Vaniyambadi. While they cleaned all the tanks, two of them who entered the last tank suffered respiratory problems and fainted as poisonous gas emanated from it, he said. Two other cleaners who tried to rescue them also suffered breathing problems and died in the tank. When another cleaner on noticing the condition of his colleagues reportedly shouted for help, Sara vanan (30), a factory helper, rushed inside the tank in a bid to save them, but he also died. The deceased were identified as C Thandrayan (37) and his brothers Elumalai (35) and Ramu (32) of CV Pattarai village near Vaniyambadi, Suryamoorthi (55) of Solur, and S Saravanan (30) of Madhunajeri village. Their bodies were recovered and sent to the Vaniyambadi government hospital for postmortem. Meanwhile agitated relatives of the deceased who gathered in front of the factory staged a road roko on the Chennai-Bangalore National Highway seeking immediate arrest of the owner of the factory for not providing safety gadgets to the cleaners. Following this traffic was hit on the highway for more than half an hour. A case has been filed and the Vaniyambadi Town Police are investigating the tragic incident