In pictures: Brazil World Cup 2014 stadium crane collapse

The accident at the Arena Corinthians, known locally as the Itaquerao, could hardly have come at a worse time — just a week before the top names in football arrive for the draw that will determine where and when all 32 teams will play in the World Cup’s opening round. Nelson Antoine / AP Photo

”The sound was as loud as a thunderclap or a huge explosion,” said Rodrigo Vessoni, a reporter with the sports newspaper Lance who witnessed the accident. Nelson Antoine / AP Photo

Firefighters recover a body of a worker who was killed. Eduardo Viana / Lancepress / AP Photo

“There was a lot of running around, a lot of shouting. It was frightening. Chills ran through my entire body.” Delfim Martins-Portal da Copa 2014 / AP Photo

World Cup preparations have been plagued by setbacks including cost overruns, stadium delays, accidents, labour strife and huge street protests in the run-up to the June tournament, once envisioned as a coming-out party for South America’s largest nation, which is also scheduled to host the 2016 Olympics in Rio de Janeiro. Eduardo Viana / Lancepress / AP Photo

Already, public prosecutors and a workers union in Sao Paulo are demanding an investigation into conditions at the work site, saying construction shouldn’t resume until authorities deem the stadium safe. Nelson Antoine / AP Photo

The newspaper Estado de S Paulo said public prosecutors had previously pointed to 50 irregularities at the venue, including some related to emergency drills. Andre Penner / AP Photo

The stadium was nearly finished before Wednesday’s accident, which occurred when a crane crashed into a 500-ton metal structure. That structure then cut through the stadium’s outer walls, destroying part of the outside of the building and slamming into a giant LED panel that runs across the facade. Nelson Antoine / AP Photo

A man takes a picture of a crane that collapsed on the site of the Arena Sao Paulo stadium, known as Itaquerao. Nacho Doce / Reuters

Soccer’s governing body said Wednesday that the “safety of workers is the top priority” to World Cup organisers and called on local authorities to “fully investigate the reasons behind such a tragic accident”. Andre Penner / AP Photo

It wasn’t the first problem with World Cup stadiums in Brazil. Three workers have died in accidents at three construction sites the past two years, and one stadium had work halted for nearly a week this year because of safety concerns. Andre Penner / AP Photo

With one thunderous crash, Brazil’s troubled preparations for the World Cup are thrown in the spotlight for all the wrong reasons, just as football gears up for the high-profile setting of the schedule for next year’s big event.

Part of the stadium that will host the tournament’s opening match collapsed Wednesday, killing two workers and aggravating already urgent worries that Brazil won’t be ready.