A worker fell 115 feet to his death from the roof of the Arena Amazonia in Brazil on Saturday, the fifth fatal accident during construction of Brazil's 12 World Cup stadiums.
Local media later reported that another worker had died of a heart attack at a convention centre next to the stadium in Manaus. The building will be used to host meeting during the World Cup.
The state's public prosecutor's office asked a judge to suspend work on the Manaus stadium until safe working conditions could be guaranteed, though such requests are not often granted in Brazil.
Marcleudo de Melo Ferreira, 22, died in a hospital in Manaus around 4 a.m. He fell nearly 35 meters (115 feet) after a cable broke and became the fifth person to die while building the World Cup stadiums.
"FIFA and the Local Organising Committee (LOC) learnt of the death of the worker on Saturday at the Arena Amazonia site with great sadness," a FIFA statement said.
Andrade Gutierrez, the Brazilian firm building the Amazonia stadium, said in another statement that Ferreira worked for a company that had been contracted to build the arena's cover and work would be suspended until Sunday.
However, the death of Jose Antonio da Silva Nascimento, 49, from a heart attack led the local construction union to threaten to strike, possibly resulting in further delays.
Fatal accidents have occurred in Manaus, Brasilia and most recently in Sao Paulo, where two people died on November 27 after a crane collapsed in the arena that is to host the opening game on June 12. <ID:L2N0JC12Z>
Another worker died while working on Palmeiras arena in Sao Paulo. While that stadium will not be used to host World Cup matches it could serve as an official training base.
The tournament will take place in 12 Brazilian cities.
Preparations for the competition - the first to be held in South America since 1978 - have been plagued by delays, accidents, cost overruns, and public anger over government waste that contributed to massive nationwide street protests last year.
The third death in less than a month again raised concerns that safety of workers was being ignored as officials rush to finish their arenas. Six stadiums are due to be delivered between now and April, and several are well behind schedule.
FIFA President Sepp Blatter last week appealed to "God, Allah and whoever" to ensure the stadiums will be ready in time.
Manaus will host four games, including the high-profile encounter between former World Cup winner England and Italy.
Image: Construction work going on at the Manaus Stadium
Photograph: Bruno Kelly/Reuters