Xcel Energy Inc. and its Colorado subsidiary were acquitted of criminal charges Tuesday in the deaths of five workers at a hydroelectric plant tunnel in the mountains west of Denver.

After nearly three days of deliberations, a jury in Denver's U.S. District Court acquitted the Minneapolis-based utility and Public Service Co. of Colorado of five counts of violating federal safety regulations, including not having a rescue plan.

The workers were trapped in the Cabin Creek plant tunnel near Georgetown, about 40 miles west of Denver, when a flammable solvent they were using to clean an epoxy paint sprayer ignited Oct. 2, 2007.

The workers communicated via radio for 45 minutes with colleagues and rescue crews. Reaching them would have involved using ropes or ladders to go down a 20-foot vertical section of tunnel, then along a 1,000-foot section at a 55-degree slope, to reach a horizontal section where the workers were. Rescuers tried lowering air tanks to the trapped workers, but the workers were overcome by smoke and fumes.

Killed were Donald Dejaynes, 43, Dupree Holt, 37, James St. Peters, 52, Gary Foster, 48, and Anthony Aguirre, 18, all of California.

Federal prosecutors had argued that Xcel knew about dangerous conditions deep inside the power plant tunnel and violated U.S. safety regulations. Xcel attorney Cliff Stricklin insisted the utility followed the law and that California-based contractor RPI Coating Inc., which employed the workers, was responsible for their safety.

Xcel and Public Service Co. each had been charged with five counts of violating Occupational Safety and Health Administration regulations. If convicted, each company could have faced fines of up to $2.5 million.