Several fans required medical treatment during Gremio's Copa Libertadores victory over Ecuador outfit Liga de Quito on Thursday, when a fence collapsed.
Former Manchester City midfielder Elano had given the hosts the lead, before portions of the home crowd proceeded to celebrate by running en masse along terraces and staircases.
The movement resulted in a human avalanche that caused one of the supporting structures to cave in, resulting in two women being rushed to hospital, as well as eight others requiring first-aid attention on the scene.
According to Globoesporte and SporTV, both women are in a stable condition, and should be released later in the morning.
This latest security breach raises further questions as to whether Brazil possesses the necessary infrastructure to support the 2014 World Cup, days after an inferno at a nightclub in neighbouring Santa Maria claimed the lives of 245 people.
Although not designated as one of the World Cup's venues - Porto Alegre's other stadium, Beira Rio, will be, with the Arena Gremio one of the nation's newest stadiums.
Chief engineer Eduardo Antonini, who oversaw the construction project, was quick to assure investigations would be carried out: "It is an engineering matter, and we want to achieve 100% safety," he told SporTV.
"We will carry out the necessary technical analysis, and look through the details calmly tomorrow. We do not want further injuries at the stadium."