Ten labourers drowned to death in sludge Saturday when an effluent treatment tank burst in Tamil Nadu's Ranipet town, officials said.Nine of the dead hailed from West Bengal and one person was from Ranipet, about 120 km from here. All were sleeping in a room adjacent to the unit that operated the CETP (common effluent treatment plant) tank.The tank burst around 3.30 a.m. Saturday and the workers drowned to death in the thick slimy effluent, an official told IANS.The unit was operating the CETP for 86 tanneries. The huge tank was at a height of around 10 feet.According to police, two people were undergoing treatment at a government hospital.In a statement issued here, Chief Minister O. Panneerselvam expressed grief over the tragedy announced a solatium of Rs.3 lakh to the families of the dead and Rs.25,000 to those injured.He said the bodies would be taken back to their native places at the Tamil Nadu government's cost.