Six contractors building Cincinnati's $400-million Horseshoe Casino did not take steps to ensure the building was stable before pouring a concrete floor atop the steel-framed structure, according to U.S. Occupational Safety and Health Administration citations issued earlier this month. The probe calls into question the roles, responsibilities and inspection procedures of the trades working on the project.

The building is a straightforward design, with beam-to-column double connections. "I think the lesson to be learned is that every structure is unique, and every structure needs new consideration for safety," says Jeffrey L. Garrett, president and CEO of CTLGroup, a Skokie, Ill.-based forensic engineer. It is not involved in the casino project.

Investigators found there were not enough bolts in place at the double connections to support the structure while concrete was being poured for the building's second floor. "The root cause was the lack of the proper amount of fasteners," says Scott Allen, an OSHA spokesman in Chicago. "OSHA issued a citation to the six companies because we feel that they were all directly involved in the erection and should have recognized the lack of proper safety standards."

The collapse occurred at a 60-ft-square bay, which broke free and fell 25 ft into a V-shape under the dead weight of wet concrete. Thirteen construction workers were injured; there were no fatalities. The building is still on schedule to open next year.

Construction manager Messer Construction Co. describes the accident as an "anomaly" in its "impeccable" safety record. The firm has participated in more than 100 OSHA inspections without a violation, notes President and CEO Tom Keckeis in a statement. The firm's last OSHA violation was in May 2006, records show.

OSHA slapped Messer with the largest penalty, levying $25,200 in fines for not implementing safety programs designed to catch the alleged mistakes, not ensuring stability during construction and not providing safe work areas. J&B Steel Erectors Inc. received the next-largest fine, at $19,600. Messer has requested a meeting with OSHA to dispute the violations, which for all the firms totaled $108,220. Officials with structural engineer THP Limited Inc. could not be reached for comment.

Such accidents are rare, says Garrett, adding, "The industry sometimes takes for granted that this work has been done and done adequately."