View of the damage at Itaquerao Stadium in Sao Paulo after a crane fell across part of the metallic structure on Wednesday. Miguel Schincariol/AFP/Getty Images

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.

The accident could delay the delivery of the stadium, in Sao Paulo, by FIFA's December deadline to have all 12 venues ready. Work was immediately halted at Itaquerao Stadium — also known as Arena Corinthians. The venue was practically completed before the collapse.

Brazilian club Corinthians, which owns the stadium, released a brief statement "lamenting" the accident. Construction company Odebrecht said it was already investigating what happened.

Former Corinthians President Andres Sanchez told a news conference that two people were confirmed dead. Local media reported a third person was hospitalized in serious condition. A fire department official had said earlier that three people had died.

Television images showed a huge metal structure buckled atop the stadium, destroying part of the stands in the east side of the venue. An LED panel installed outside the venue was also hit.

The accident apparently occurred when a crane collapsed on top of the metal structure. The crane was installing what was the last part of the structure. Because the accident happened at lunchtime, not many workers were on the site when it occurred.

Itaquerao Stadium will seat nearly 70,000 people for the opener on June 12. The venue is scheduled to host five other matches, including a semifinal. It was initially expected to be built for the Confederations Cup this year, but financing delays prompted authorities to eliminate the stadium from the World Cup warmup tournament.

Brazil is racing against time to deliver the last six World Cup stadiums by the end of the year, although work at Itaquerao was advanced compared with the other venues.

"FIFA and the LOC (Local Organizing Committee) have learnt of the death of workers at the Corinthian's Arena site in Sao Paulo with great sadness," FIFA wrote in a statement. "We wish to send our heartfelt condolences to the family of the workers who tragically died today."

Soccer's governing body said the "safety of workers is the top priority" to World Cup organizers.

"We know the safety of all workers has always been paramount for all the construction companies contracted to build the 12 FIFA World Cup stadiums," it said. "The local authorities will fully investigate the reasons behind such a tragic accident."

FIFA President Sepp Blatter said he was "deeply saddened by the tragic death of workers" at the stadium. "Our heartfelt condolences are with the families," he said.

FIFA Secretary-General Jerome Valcke said he was "extremely shocked by the news from Sao Paulo."

"Our thoughts are with the families of the victims of this accident," he said.

The Associated Press