Xcel Energy knew about dangerous conditions deep inside a Colorado power plant tunnel where five maintenance workers died of smoke inhalation in a 2007 blaze, and it violated U.S. safety regulations by ignoring them, a federal prosecutor charged…Xcel attorney Cliff Stricklin insisted the utility followed the law and that a California-based contractor that employed the workers was responsible for their safety. Stricklin told jurors that prosecutors were using hindsight to try to hold the defendants to a standard of perfection…Xcel and Public Service Company are each charged with five counts of violating Occupational Safety and Health Administration regulations for the October 2007 fire inside a water tunnel at a hydroelectric plant…If convicted, each company could pay fines of up to $2.5 million.