The victims fell through a hole that suddenly opened beneath their feet Sunday night at the Fonte Nova stadium in the northeastern coastal city of Salvador as fans jumped up and down at the end of a game.
Police initially said eight people were killed, but the government of Bahia state where Salvador is the state capital on Monday said seven died and several were hospitalized with severe injuries.
The victims fell 15 meters (49 feet) through a 3-meter- (10-foot-) wide hole, Bahia state's secretary of sports, Nilton Vasconcelos, told the official Agencia Brasil news agency.
Vasconcelos said it was not clear why collapse happened, but the 56-year-old stadium was recently highlighted as the worst of 29 soccer venues across Latin America's largest nation in a survey conducted by a Brazilian association of engineers and architects.
The accident happened as the game ended, when fans of the Bahia soccer team went into a wild celebration, storming the field because their team managed a goalless draw with Vila Nova, securing Bahia a place in the nation's second division.
Fans were jumping up and down in glee when the hole opened in the concrete floor of the stand. The victims fell several stories.
About 60,000 people were at the stadium for the game, and many didn't realize that the section of bleachers had given way as they invaded the field in celebration.
The stadium was built in 1951, and the soccer stadium survey released last month by Brazil's Sinaeco association of architects and engineers said Fonte Nova's stands were "in ruins."
The group's report also featured pictures of crumbling support beams under the stands, and characterized Fonte Nova overall in "pitiful state, (with) no comfort or security for users."
The survey was conducted because Brazil will host the 2014 World Cup, and the association wanted to give authorities an idea of what sort of improvements are needed to make the tournament a success. Salvador would almost certainly get some of the games.
Brazil, which has won a record five World Cups, was awarded the right last month to host the 2014 tournament by FIFA, soccer's governing body. Latin America's largest country hosted the competition once before, in 1950.
The state governor of Bahia state, Jacques Wagner, ordered the Fonte Nova stadium closed while authorities investigate the cause of the accident.
Vasconcelos said the stadium has undergone renovations in the past, but that none of them dealt with its structural integrity.
Before the accident, Bahia state officials were considering a renovation of Fonte Nova to host World Cup games. They were also looking into the possibility of building a new stadium for Salvador, a major Brazilian tourism destination.