ONE of the largest mobile cranes in the United States collapsed at a Houston oil refinery in Texas on Friday, killing four workers and injuring seven.

It was the latest of several fatal accidents that have raised concerns about the safety of construction cranes.

The 30-story-tall crane, capable of lifting 450,000 kilograms, fell over at a LyondellBasell refinery in southeast Houston about 2pm local time, said Jim Roecker, the company‘s vice president for refining.

The crane fell on a tent which Houston television station KTRK-TV said was used for worker meals.

After the incident, the massive red crane lay on top of a smaller, bright yellow crane on the grounds of the refinery. Ambulances and fire trucks were lined up outside.

The casualties were in the area of the crane, but officials were still are not certain whether they were on the crane or under it, Roecker said.

Three of the injured were treated and released at the scene, said Houston Fire Department Assistant Chief Omero Longoria.

Two severely injured workers were taken by helicopter to Memorial Hermann-Texas Medical Center hospital and the other two injured workers were taken to a hospital by ambulance.

Roecker described the collapsed cranet as one of the largest mobile cranes in the US, at 91 meters tall with a 122-meter boom. Construction cranes can be taller, but they are not mobile.

In addition to the coking unit, a crude distillation unit had been shut at the refinery for a planned seven-week overhaul. The refinery has two coking units and two crude units.

Refinery spokesman David Roznowski declined to discuss the refinery‘s current level of production. He said it would be at least several days before Lyondell could determine how the crane collapse would affect the planned overhaul.

Roecker said the crane was operating, but was not lifting anything.

"It certainly is too early to tell what caused the issue," he said.

Tent smashed



KTRK-TV interviewed a man at a Houston hospital who was identified as one of the injured workers.

"All I saw was our lunch tent was smashed," Michael Gabriel told the station.

The crane collapse in Houston was the deadliest US crude oil refinery accident since a 2005 explosion at BP Plc‘s giant refinery in Texas City killed 15 workers and injured 180 others. Texas City is 80 kilometers south of Houston.

Following a two-year investigation of the BP blast, the US federal Chemical Safety Board recommended that refiners not place workers in structures near process units incapable of withstanding catastrophic explosions.

The fatalities in Houston follow two recent deadly crane collapses in New York. In May, two people were killed on Manhattan‘s Upper East Side after a large crane fell and damaged an apartment building. In March, seven were killed after a crane crushed a residential building.

Roecker declined to disclose the names of those killed and the companies for which they worked, pending notification of their next of kin.

Crane owner Deep South Crane & Rigging said in a statement that it had few details about the accident.

"Our thoughts and prayers are with our employees and their loved ones," the company said.

Those killed and injured worked for outside contractors involved in the overhaul of one of two coking units and one of two crude distillation units at the refinery. The work began in early July.

Aerial views of the site were not immediately available yesterday, as air space around Houston was restricted because President George Bush was in town raising funds for a congressional candidate.

LyondellBasell is a Netherlands-based chemical and refining company with annual revenues of US$45 billion and 16,000 employees worldwide.