AP Wideworld
Two people died in a Nov. 27 accident that toppled a crawler crane and part of the Itaquerao stadium, future site of the opening of the World Cup 2014 in Brazil.

A leading expert on crane collapses describes a Nov. 27 accident at a World Cup soccer stadium under construction in Brazil as "highly unusual" after an initial assessment of damage photos.

"It is unusual because the boom snapped off the car body," says Jim Wiethorn, a forensic specialist at Haag Engineering, Sugar Land, Texas. "The boom and mast are intact but the pins [which hold the boom to the crane] are gone. All the holes are there and not damaged, yet the boom is gone."

The crane was carrying a section of roof for the soccer stadium under construction in São Paulo, Brazil, when it collapsed the afternoon of Nov. 27, killing two workers. Arena Corinthians, also referred to as Itaquerão stadium, is slated to host the opening game of the soccer spectacle on June 12, 2014.

The Liebherr model LR11350 crawler crane that fell is believed to be the largest of its kind in operation in South America. It has a 1,350-tonne maximum load capacity and a maximum boom length of 228 meters. The more than 200,000-square-meter site is located on the east side of São Paulo at the former training facility for the Corinthians soccer team.

The $360-million stadium is owned by Sport Club Corinthians Paulista, and construction is being handled by the Brazilian firm Odebrecht. The construction team has confirmed in a joint statement that the crane collapsed shortly before 1 p.m. while hoisting the final 420-ton module of the metal roof into place over the stadium's north stands.

The roof portion struck a part of the east building and partially damaged the massive LED panel that runs across the structure's facade. Two construction workers, Fábio Luiz Pereira, 42 years old, and Ronaldo Oliveira dos Santos, 44, were killed in the collapse. Officials say the grandstand itself was not compromised by the accident.

Officials with Odebrecht and Sport Club Corinthians said they were working with authorities investigating the accident and that the cause of the collapse has not been identified.

The lifting procedure, which involved hoisting the module to a height of 40 meters, was described by the company as "routine," having been performed more than three dozen times before Wednesday's incident. According to Odebrecht, the procedure required a team of 65 specialists a total 72 hours to complete.

While rain had delayed the placement of the final section of the roof, meteorologists said there was no wind or rain at the site during the time of the accident.

Work on the 70,000-seat venue began in 2011, and it was 94% complete at the time of the accident. FIFA, the world soccer organizing body, has set a year-end deadline for the completion of the stadiums hosting the World Cup.

Odebrecht said work on the arena will resume next Monday.