Twelve shanties were guttedand many damaged, leaving 70 people homeless as a fire broke out at a slum in Kamarhati area near Kolkata, officials said.The fire was caused by a short circuit, which led to the explosion of a gas cylinder, they said.Three fire engines took two hours to douse the blaze, the officials said.Kamarhati Municipality chairman Gopal Saha said the civic body has arranged relief and a temporary shelter for those affected in the fire.