CHEYENNE - An investigation into the cause of a crane accident that injured three workers at a coal mine in northeastern Wyoming over the weekend could take months, a spokesman for the Federal Mine Safety and Health Administration said today.

Two ironworkers remain hospitalized at the Wyoming Medical Center in Casper. One man was listed in critical but stable condition, and the other in stable condition.

Bill Denning, a spokesman for MSHA in Denver, said federal investigators, including a structural engineer from Pennsylvania, were at the scene of the accident today. The agency shut down the construction project where the accident occurred, but coal-mining operations were ongoing.

"We won't reach any conclusions for months," Denning said. "There's going to have to be a lot of testing done."

The crane collapsed Saturday afternoon while it was lifting a 280-foot section of conveyor tube to place it on supports above railroad tracks at the Black Thunder coal mine near Wright, about 180 miles north of Cheyenne. The tube is part of a two-mile long, 6-foot wide conveyor system that will deposit coal into silos for loading onto train cars.

Terry Adcock, Wyoming State Inspector of Mines in Rock Springs, said investigators have yet to find any indication of what caused the accident.

"I don't think anybody's got any major point on why," said Adcock, who went to the site over the weekend. "Hopefully by the end of this week, we'll have a better idea of what caused the failure."

For more, see Tuesday's Casper Star-Tribune.