The first real concern emerged after a video of a temporary walkway wobbling under the weight of hundreds of fans at the Maracana in Rio de Janeiro after the Argentina game.
"When people walk on it the wood moves, so with thousands of people walking up there, there could be an accident," a fan told the Associated Press.
Yahoo's Cody Brunner reports that the stairs were still under construction a few days before the match.
"The boards are cobbled together in a way that boards teeter when even one person uses the staircase," he wrote.
Chile and Spain play at the Maracana on Wednesday night.
The video is scary: