The first body was removed at 3:45 p.m. and it was expected to take 40-45 minutes for each body from more than 1,500 feet from the entrance at Excel Energy's Cabin Creek power plant. Officials had not identified any of the victims, whose bodies were not found together, the Rocky Mountain News reported.

The cause of the Tuesday blaze had not been determined.

Authorities said the who died and four co-workers who escaped were employees of RPI Coating of Sante Fe Springs, Calif. The company, which had been hired by Excel to paint the inside of a large pipe, had a history of workplace violations, the newspaper reported.

"We always ensure that our workers are working in a safe environment," Xcel spokesman Tom Henley said. "However, again, these were contractors and they are experts in this industry. And that's why we hired them."

An RPI spokesman could not be reached for comment Wednesday, but a California OSHA employee said the company may still be appealing some of the complaints.