[img]http://d.yimg.com/a/p/ap/20100207/capt.f57db769c7e44efb82ef219078aea6ad.middletown_explosion_hfd107.jpg?x=121&y=130&q=85&sig=lXgOludMGyAzIgpubATx9A--[/img]AP - An explosion that sounded like a sonic boom blew out walls of an unfinished power plant and set off a fire during a test of natural gas lines Sunday, killing at least five workers, injuring a dozen or more and leaving crews picking through debris for more possible victims.