GEORGETOWN, Colo. -- Federal investigators have focused on working conditions and safety procedures inside the hydroelectric plant tunnel where five workers died Tuesday after a fire erupted on the equipment they were using.

Autopsies were expected to be completed by Monday or Tuesday, but authorities believe smoke and fumes from the fire killed the workers as they sat trapped deep underground. Communication from the crew ended about an hour after the fire broke out.

The bodies, found scattered along a 200-foot length of the 12-foot-wide pipe, didn't have burn marks, indicating that the men probably died from the smoke and fumes from the chemical fire, Undersheriff Stu Nay said.

The dead workers were all from California and have been identified as Donald Dejaynes, 43; Sun City; Dupree Holt, 37, of Ontario; James St. Peters, 52, hometown unknown; Gary Foster, 48, of Bakersfield; and Anthony Aguirre, 18, of Mira Loma.

The bodies were taken to the Jefferson County coroner's office in Golden, 30 miles east of Georgetown. Clear Creek County Coroner Don Allan said autopsies will be completed early next week.

OSHA was looking at what kind of protection and safety training the maintenance crew had; safety procedures for the type of work being performed inside the tunnel; and documentation that safety procedures were being followed, agency spokesman Rich Kulczewksi said.

The OSHA probe was expected to take months and involve federal, state and local agencies, said the agency's Denver area director, Herb Gibson.

"We want a thorough investigation that will ensure this type of incident will never occur in the future when people are working in confined spaces," Gibson said.

Investigators were interviewing personnel from Xcel Energy, which operates the plant; RPI Coating Inc. of Santa Fe Springs, Calif., which was hired to apply an epoxy and paint coating to the inside of the tunnel; and KTA-Tator Inc., a Pittsburgh-based consulting and engineering firm hired by Xcel to inspect the work.

Tom Cisneros, who escaped the tunnel after the fire broke out, was interviewed by investigators.

"Those were my brothers. We were all family, tightknit," Cisneros said. "We were all trained and it was an accident."

Xcel spokeswoman Ethnie Groves could not confirm whether KTA-Tator had any employees at the scene when the fire broke out, and she declined to release additional information.

Bruce Rutherford, KTA-Tator coatings business operations manager, declined to comment and referred calls to Xcel.

Nay said workers were experiencing trouble with a spray gun used to apply the epoxy and paint mixture and were adding a solvent to a hopper used to warm up the mixture to liquify it for application. The hopper's heating element inadvertently turned on, igniting the vapors.

The five workers scrambled past a bulkhead used to keep their work area dry and radioed to their co-workers that they were OK, except for minor injuries, but fire blocked their downhill escape route. The 55-degree incline of the tunnel above them kept them trapped more than 1,500 feet below ground.

Then the radio went dead.

The Clear Creek Sheriff's Office released 911 calls about the fire, which were dramatic but didn't reveal any detail that hasn't been known.

In one tape, Bob McGurk, a Control Specialist at Cabin Creek is heard.

"We have a fire in our penstock, in our tunnel," he said. "I've got a chemical fire 1,000 feet underground ... There are people trapped."

Officials lowered breathing masks and air tanks and a spare radio to the men, but the smoke might have kept them from seeing the items.

Emergency crews reached the workers six hours later, about a half-mile from the tunnel's bottom exit.

Authorities have defended their rescue efforts, saying smoke, the complexities of the 4,000-foot tunnel's design and uncertainties about the dangers kept them from successfully entering the tunnel for more than 3 1/2 hours after the blaze broke out.

One crew went in about 1 1/2 hours after the fire broke out but had to turn back because of the smoke, Nay said.

Four RPI Coating workers escaped from the tunnel, which delivers water from a reservoir to turbines that generate electricity at the plant 30 miles west of Denver.

Xcel Energy is coordinating its own investigation into the fire with OSHA, Groves said. It wasn't known how long plant operations might be affected. Maintenance had been scheduled to last until mid-November.