At least two people have been killed in a partial collapse at the stadium due to host the World Cup opener in Brazil next year.

Part of the grandstand was destroyed when a metal structure buckled at the top of the Arena Corinthians venue in Sao Paulo.

Local media reported that the accident was caused by a crane collapse. Construction work has been halted at the site.

The stadium is owned by Sport Club Corinthians Paulista, with building work on the venue carried out by the industrial conglomerate Odebrecht SA.

In a joint statement, Corinthians and Odebrecht said that at least two workers had died.

They have been named as Fabio Luiz Pereira, 42, and Ronaldo Oliveira Dos Santos, 44.

"Teams of firemen are in place. At the moment, all efforts are focused to provide full assistance to the families of the victims," the statement said.

Fire official Mauro Lopes had earlier said in a radio interview that at least three people died in the accident.

The accident happened at lunchtime, so not many workers were on site at the time. Of the 1,700 people who usually work at the stadium, only 30 were on site at the time of the accident.

The collapse could delay the delivery of the stadium - which was almost complete - in time for FIFA's December deadline.

Brazil has struggled to deliver stadiums, public transportation improvements and other World Cup-related projects within the timelines specified by FIFA.

Some construction sites, such as a new terminal at Sao Paulo's international airport, are being built around the clock seven days a week to try to finish them before the Cup.

The venue is due to host the World Cup opener and five other matches.

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

FIFA said, "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.

"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".

"Our heartfealt condolences are with the families," he said.