CHEYENNE - Two ironworkers remained hospitalized Sunday, one in critical condition, with injuries they suffered in a crane accident at a northeast Wyoming coal mine.

TIC Wyoming Inc. said two of its employees - Andrew Milonis and Frederico Salinas - were being treated at Wyoming Medical Center in Casper. Milonis was listed in critical but stable condition, and Salinas was listed in stable condition, said Mike Chambers, a nursing supervisor at the hospital.

Three workers were injured Saturday afternoon when a large crane collapsed as it was setting a 280-foot section of conveyor tube on supports above railroad tracks at the Black Thunder coal mine near Wright, about 180 miles north of Cheyenne.

TIC Wyoming, a heavy industrial contractor based in Casper, said the cause of the accident was still under investigation on Sunday.

The Mine Safety and Health Administration, which suspended the mine's operation on Saturday, was investigating the accident on Sunday, along with TIC, mine owner Thunder Basin Coal Company and Lampson International, the owner of the crane, according to a release from TIC.

Messages left with spokesmen for the Mine Safety and Health Administration and the Wyoming Division of Mine Inspection and Safety, and for the safety manager at Black Thunder were not returned Sunday afternoon.

The third injured worker was Rodney Loffler, a crane hoist operator employed by Lampson, said Bruce Stemp, the crane company's director of safety. Loffler, who worked out of the company's Denver office, suffered contusions and stress fractures to some of his vertebrae, Stemp said. He was released Sunday from the Campbell County Memorial Hospital in Gillette, a nursing supervisor said.

About 150 TIC employees have been working on the construction project at the coal mine, which is situated in the Powder River Basin, the nation's most productive coal basin. The company is building a system to move coal from the mines to railroad cars, with components including a truck dump, coal-crushing facilities, a 2-mile long 6-foot wide conveyor system, a silo head house and train loadout system.

Saturday's accident blocked three tracks of a main railroad line jointly operated by BNSF Railway and Union Pacific, said Gus Melonas, spokesman for Fort Worth, Texas-based BNSF. Service was restored on the three main lines by Saturday night, but the broken crane and debris from the conveyor tube were still blocking a connection off the main line that serves the Black Thunder and Jacob Ranch mines on Sunday. The mines were accessible by other lines, Melonas said.

TIC didn't have information on the hometowns or ages of injured workers Milonis or Salinas. The company said it was providing transportation, lodging and other assistance to the families of its injured employees.

"We will stay in close contact with family members and medical personnel to monitor the medical progress of our employees, and to assure that their needs are being met," TIC Wyoming President Dean Brister said in a written statement.