SAO PAULO (AP) — 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.

Brazil has been plagued by a series of setbacks including cost overruns, stadium delays, accidents, labor strife and massive 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 Olympics in 2016.

Wednesday’s accident at Sao Paulo’s Itaquerao stadium 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 accident could delay delivery of the stadium, which was practically finished before Wednesday’s collapse. FIFA has set a December deadline for all 12 World Cup venues to be ready. The World Cup begins on June 12 with Brazil playing at the Sao Paulo stadium.

Officials said there were no major structural damages to the stadium but declined to say how much the accident may affect the delivery.

“I don’t want to know about FIFA right now, we are worried about the families of the victims,” former Corinthians president Andres Sanchez told a news conference.