• Two deaths at Arena da Amazônia in recent days • End-of-year deadline unlikely to be met for England venue

A strike over safety conditions following a fatal accident has halted already-overdue construction of the Manaus stadium where England are due to play their opening World Cup match.

After the death of two workers last week, the builders' union have downed tools, saying the rush to finish the job before the year-end deadline is putting lives at risk. "The rating for safety in the building site is zero … and we're under constant pressure to work," the builder José Aristoteles de Souza Filho told the Brazilian news website G1.

The strike is the latest setback for the Arena da Amazônia, which is among several World Cup venues that are behind schedule. At the weekend, a court ordered the suspension of work on the roof of the basket-shaped stadium after a worker, fell 35 metres to his death on Saturday. Marcleudo de Melo Ferreira died after his cable snapped in the early hours at the end of a night shift.

The previous weekend, the Guardian saw frenetic activity at the site where almost 2,000 workers are working around the clock to finish the task of installing the giant steel girders that make up the lattice structure. It was said at the time to be only 95% complete.

Locals said the task had been delayed by the late arrival of the steel, which has had to be shipped from Portugal to the heart of the Amazon.

Another worker died of a heart attack on Saturday that the bereaved family claim was induced by stress. It was the third fatality this year at the site.

During the court case on Saturday, prosecutors called for the $200m project to be halted until an updated safety report is produced by the construction firm Andrade Gutierrez. In a warning that the contractors could also be fined, the prosecutors office noted in a statement that it "cannot allow the urgency of finishing construction for the 2014 World Cup to be at the cost of the life and wellbeing of those working on it".

Andrade Gutierrez has sent investigators to the site and issued a statement of regret. "We reiterate our commitment to [ensuring the] security of everyone working at the site," the company said in a statement.

Fifa has also expressed condolences for the death, which is likely to add to criticisms that the economic and human cost of the World Cup is excessive. At least five workers have died so far. Most of the fatalities have come in the past few weeks as the pressure to finish on time increased.

Last month, two workers were killed in São Paulo when a crane collapsed at the Corinthians Arena, which is scheduled to host the opening game of the World Cup. Officials say the venue will not be ready until April, barely two months before the tournament starts.

Manaus officials said there were unsure when work will recommence on the Arena da Amazônia. But it now looks certain to drag on well into the new year.