Part of the stadium that will host the 2014 World Cup opener in Brazil collapsed on Wednesday, causing significant damage and killing at least two people, authorities said. Firefighters recover the body of a worker who was killed when a part of the Itaquerao stadium collapsed, in Sao Paulo, Brazil, Wednesday, Nov. 27, 2013. Part of the stadium that will host the 2014 World Cup opener in Brazil collapsed on Wednesday, killing two workers and raising urgent new concerns whether the country will be ready for soccer's signature event. AP Photo/ Eduardo Viana/Lancepress A collapsed metal structure sits on the ground at Itaquerao Stadium in Sao Paulo, Brazil, Wednesday, Nov. 27, 2013. The accident that resulted in the death of at least two workers, occurred when a construction crane crashed into a 500-ton metal structure that in turn cut through the outer walls of the venue, destroying rows of seats and slamming into a massive LED panel that runs across the stadium's facade. The stadium is slated to host the 2014 World Cup opener. A metal structure that buckled sits on part of the Itaquerao Stadium in Sao Paulo, Brazil, Wednesday, Nov. 27, 2013. SAO PAULO (AP) - With one thunderous crash, Brazil's troubled preparations for the World Cup are thrown in the spotlight for all the wrong reasons, just as soccer 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. "It was a huge explosion," said 32-year-old stonemason Evandro Pereira, who was off at a cafeteria at the time of the lunchtime accident. It was really very scary. We all ran out and we were shocked to see the crane had collapsed on top of the stands. 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 soccer arrive for the draw that will determine where and when all 32 teams will play in the World Cup's opening round. "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. World Cup preparations have been plagued by setbacks including cost overruns, stadium delays, accidents, labor 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. 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. Ricardo Trade, CEO of the local World Cup organizing committee, said authorities would determine if there is a need to suspend construction. There are seven months till the World Cup, not 10 days, so I don't believe this is going to cause delays. But there is absolutely no guarantee on this," Trade said in a telephone interview. The accident could lead to recriminations between local organizers and world soccer's organization FIFA, which has set a December deadline for all 12 World Cup stadiums to be ready. The tournament begins June 12. "I don't want to know about FIFA right now; we are worried about the families of the victims," said Andres Sanchez, former president of the Sao Paulo soccer club Corinthians, which is building the stadium. The club said workers would not return before a three-day mourning period. The newspaper Estado de S. Paulo said public prosecutors had previously pointed to 50 irregularities at the venue, including some related to emergency drills. 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. Sanchez said it appeared the structure of the stadium was not compromised, meaning there should be enough time to recover before the World Cup. Six stadiums have already been declared ready for the games. But Brazil is still racing to finish the other six, and there is particular concern that the stadiums in Cuiaba, Manaus and Curitiba may not be ready by the end of December. FIFA has said it would not accept the same delays that plagued stadium construction before soccer's Confederations Cup earlier this year, for which only two stadiums were ready on time. Soccer's governing body said Wednesday that the "safety of workers is the top priority" to World Cup organizers and called on local authorities to "fully investigate the reasons behind such a tragic accident." One of the dead workers, 42-year-old Fabio Luis Pereira, was inside a truck that was hit by the fallen metal structure. The other, 44-year-old Ronaldo Oliveira dos Santos, was taking a break in an area that was supposed to be clear. "Unfortunately nobody saw him," Sanchez said. He was napping. 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. Associated Press writers Stephen Wade and Jenny Barchfield in Rio de Janeiro contributed to this report. Tales Azzoni on Twitter: http://twitter.com/tazzoni