The Arena, also known as Itaquerao stadium, is still missing some 20,000 temporary seats on the bleachers, according to Odebrecht, the company in charge of the construction, Xinhua reported.
The stadium will host the opening match of the World Cup with host Brazil against Croatia on June 12.
The temporary bleachers are expected to be fully completed by mid-May when FIFA will officially take over all operations in the stadium.
The construction of the Itaquerao stadium was marked by a series of problems. In November, a large accident killed two workers and destroyed part of the bleachers, significantly delaying construction. And in March, another worker died on the construction site.
The World Cup will take place in 12 Brazilian cities from June 12 to July 13.
This will be the second time Brazil hosts a World Cup, with the first in 1950.