A construction worker was killed and two others were injured on Wednesday when their attempt to waterproof a basement and install a mikve (Jewish ritual bath) caused an explosion strong enough to blow out a wall in a home, the fire department said. Witnesses described a furious blast that shook nearby homes, knocked out windows and covered the Brooklyn neighborhood in smoke. They said at least one victim stumbled out of the house naked and on fire. City officials said the homeowners did not have a permit to install the mikve. Firefighters at the scene said the basement did not have proper ventilation.