(Click here for the Star-Tribune's video story on the installation of the Black Thunder crane in April.)

UPDATE June 2, 2008: Two remain hospitalized. Click here for the story.

GILLETTE - The world's largest crane in handling capacity collapsed Saturday near Wright, sending three injured people - two critically - to hospitals and blocking a rail line at the Black Thunder coal mine.

Federal Mine Safety and Health Administration inspectors and crane company representatives were traveling to the mine, and BNSF Railway crews were expected to clear the tracks by late Saturday.

The names of the injured, who they worked for or what their jobs were wasn't immediately known.

The 2.7 million-pound crane, owned and operated by the Kennewick, Wash.-based Lampson International, was moved to the site in April.

On Saturday, it was moving a 260-foot, 500,000-pound section of tubing over the triple-track main railroad line - jointly owned by BNSF Railway and Union Pacific - when the accident occurred at 12:20 p.m., said Fort Worth, Texas-based BNSF Railway spokesman Gus Melonas.

A 70-foot section of the tubing blocked the tracks, and material and debris were also blocking a connection off the main line that serves the Black Thunder and Jacob Ranch mines, Melonas said.

"We did shut down railroad traffic," he said.

The tubing was to enclose a large conveyor over the railroad. The conveyor system will also reach over the Hilight Road to the top of two new coal silos for Black Thunder, which is owned by Arch Coal Inc.

Arch Coal Inc. spokesman Greg Schaefer said the company will assess the damage after crews clear the wreckage.

No railroad or mine personnel were hurt, Melonas and Schaefer said.

Even so, Thunder Basin mine security officer Truman Cavender said he was ordered to call ambulances to the new construction site, which is seven miles from the mine's headquarters.

Two of the injured were described as very critical, said Wright resident and Campbell County Sheriff's Deputy C.T. Akers.

One was taken to the Wyoming Medical Center in Casper, said nursing supervisor Mike Chambers, who did not release any information on the person's identity or the severity of injuries.

Campbell County Memorial Hospital in Gillette was expecting to receive two patients, said nursing supervisor Debbie Rhoades, adding she didn't know how serious their injuries were.

Akers, who arrived at the scene about 15 minutes after hearing of the accident, said the collapse caused extensive damage to the crane.

"It's completely toppled over; it's a mass of blue, twisted metal," he said. "My guess would be that they might be able to salvage the power unit and the tracks, and things like that. But the gantry, that's going to be scrap metal, would be my guess."

A mine spokesman said TIC is the general contractor for the job, and EarthWork Solutions is doing dirt work for the job.

Bill Denning, spokesman for the Mine Safety and Health Administration in Denver, said the mine will be shut down while agency officials conduct an investigation.

Bruce Stemp, director of safety for Lampson International in Washington state, said company representatives were on their way to the scene.