Construction Worker Hurt When Arm of Crane Snaps : Accident: The boom was lifting a huge concrete slab. A foreman at the site suffers broken bones and facial cuts.

A construction worker was injured at Torrance Municipal Airport on Tuesday when a boom lifting a concrete wall snapped and narrowly missed pinning the man under the huge cement slab.

More than half a dozen other workers at the site fled after hearing a loud noise while one of the walls for a new flight-test facility being built for Robinson Helicopter Co., the nation’s largest supplier of commercial helicopters, was being lifted by the crane.

Allen Hansel, a foreman with a crane rental service, was struck by the boom and some heavy cables, officials said. He was treated by paramedics at the scene for a fractured hand, a broken toe and severe facial cuts and taken to the trauma unit at Harbor-UCLA Medical Center. He was listed in stable condition.

“I just heard a snap, and then everybody just took off running,” said construction site worker Tom Egan. “When you hear a noise like that you don’t bother to see what it is, you just take off running.”

Torrance Fire Battalion Chief Gerald Goins said the accident occurred shortly after 10 a.m. when the workers raised the wall using a 100-foot-long boom. The crane arm snapped, sending the slab plummeting. Officials reported the accident to Cal-OSHA investigators, who closed the site Tuesday. It was reopened Wednesday. The cause of the accident is still under investigation.

“All we know is that they had some kind of mishap or mechanical failure,” Goins said. “The wall came down, and some piece of the equipment apparently struck the foreman, who was providing visual signals to the crane operator.”

Construction workers at the scene all reported hearing a loud noise, and several site employees were nearly struck by the wall. When it hit the ground, it sent a huge dust cloud over the area and stunned nearby airport workers.

The mobile crane was certified to lift 150 tons and was inspected two months ago, according to company officials. Although they did not know how much the concrete slab weighed, officials said it was less than 150 tons.

“It’s amazing that nobody else was hurt,” one unidentified construction worker said. “Between the boom and the wall, there was enough there to kill several people.”

The new 33,000-square-foot building will be used for flight tests for Robinson, which is building a larger version of its well-known R-22 helicopter. The facility is expected to be completed in August.